Update UART pin names & add MBED_CONF_TARGET_STDIO_UART overrides

Add standard pin-names validation script & tests

Add bare metal support to EFM32 targets ...

Modify scatter files to add heap load region, and remove hard coded
values. Add supported c libs and bare metal profile to `targets.json`
configurations. Affects the following targets: EFM32GG_STK3700,
TB_SENSE_12, and EFM32GG11_STK3701.

Remove uARM dependencies for EFM32FF targets

CMake: Refactor Silicon Laboratories targets ...

Refactor all Silicon Laboratories targets to be CMake buildsystem targets. This removes
the need for checking MBED_TARGET_LABELS repeatedly and allows us to be
more flexible in the way we include MBED_TARGET source in the build.

A side effect of this is it will allow us to support custom targets
without breaking the build for 'standard' targets, as we use CMake's
standard mechanism for adding build rules to the build system, rather
than implementing our own layer of logic to exclude files not needed for
the target being built. Using this approach, if an MBED_TARGET is not
linked to using `target_link_libraries` its source files will not be
added to the build. This means custom target source can be added to the
user's application CMakeLists.txt without polluting the build system
when trying to compile for a standard MBED_TARGET.

EFM32GG: Fix heap size formula in scatter files ...

The heap size was incorrectly calculated.
This fixes it by subtracting the Stack size, any memory chunks allocated
before the start of the application (for vectors and/or crash report), and
finally the size of the application from the total RAM size.

CMake: Add support for SiLabs EFM32GG targets

stack: armc: Workaround config passing bug ...

Workaround a bug where the boot stack size configuration option is not
passed on to armlink, the Arm Compiler's linker. Prefer
MBED_CONF_TARGET_BOOT_STACK_SIZE if present, as this is what the
configuration system should provide. Fall back to MBED_BOOT_STACK_SIZE
if MBED_CONF_TARGET_BOOT_STACK_SIZE is not defined, as in the case of
buggy tools. If both MBED_CONF_TARGET_BOOT_STACK_SIZE and
MBED_BOOT_STACK_SIZE are not defined, then we fall back to a hard-coded
value provided by the linkerscript. See
https://github.com/ARMmbed/mbed-os/issues/13474 for more information.

Use boot stack size from config system ...

To allow overriding of the boot stack size from the Mbed configuration
system, consistently use MBED_CONF_TARGET_BOOT_STACK_SIZE rather than
MBED_BOOT_STACK_SIZE.

Fixes #10319

EFM32: move __Vectors from header to source

EFM32: update emlib for EFM32GG

modified itm_api.c for STK3701 and add SWO location 0 to EFM32GG11_STK3701, EFM32GG_STK3700, EFM32LG_STK3600, EFM32PG_STK3401, EFM32PG12_STK3402 and EFM32WG_STK3800

Clean up ARM toolchain heap+stack setup in targets ...

ARM Compiler 6.13 testing revealed linker errors pointing out
conflicting use of `__user_setup_stackheap` and
`__user_initial_stackheap` in some targets. Remove the unwanted
`__user_initial_stackheap` from the targets - the setup is
centralised in the common platform code.

Looking into this, a number of other issues were highlighted

* Almost all targets had `__initial_sp` hardcoded in assembler,
  rather than getting it from the scatter file. This was behind
  issue #11313. Fix this generally.
* A few targets' `__initial_sp` values did not match the scatter
  file layout, in some cases meaning they were overlapping heap
  space. They now all use the area reserved in the scatter file.
  If any problems are seen, then there is an error in the
  scatter file.
* A number of targets were reserving unneeded space for heap and
  stack in their startup assembler, on top of the space reserved in
  the scatter file, so wasting a few K. A couple were using that
  space for the stack, rather than the space in the scatter file.

To clarify expected behaviour:

* Each scatter file contains empty regions `ARM_LIB_HEAP` and
  `ARM_LIB_STACK` to reserve space. `ARM_LIB_STACK` is sized
  by the macro `MBED_BOOT_STACK_SIZE`, which is set by the tools.
  `ARM_LIB_HEAP` is generally the space left over after static
  RAM and stack.
* The address of the end of `ARM_LIB_STACK` is written into the
  vector table and on reset the CPU sets MSP to that address.
* The common platform code in Mbed OS provides `__user_setup_stackheap`
  for the ARM library. The ARM library calls this during startup, and
  it calls `__mbed_user_setup_stackheap`.
* The default weak definition of `__mbed_user_setup_stackheap` does not
  modify SP, so we remain on the boot stack, and the heap is set to
  the region described by `ARM_LIB_HEAP`. If `ARM_LIB_HEAP` doesn't
  exist, then the heap is the space from the end of the used data in
  `RW_IRAM1` to the start of `ARM_LIB_STACK`.
* Targets can override `__mbed_user_setup_stackheap` if they want.
  Currently only Renesas (ARMv7-A class) devices do.
* If microlib is in use, then it doesn't call `__user_setup_stackheap`.
  Instead it just finds and uses `ARM_LIB_STACK` and `ARM_LIB_HEAP`
  itself.

Heap and stack size picked from linker files,export symbols not needed

Guard RAM start and size defines

Target_SiLabs: Add ARM_LIB_STACK and ARM_LIB_HEAP section ...

Instead of user defined symbols in assembly files or C files,
use linker scripts to add heap and stack - this is inconsistent
with ARM std linker scripts

[Silicon_Labs] Support boot stack size configuration option

SiLabs: Fix alignment of execute region to 8-byte boundary ...

--legacyalign, --no_legacyalign are deprecated from ARMC6 compiler, in order to
remove deprecated flags all linker files (GCC and IAR as well to have uniformity)
should strictly align to 8-byte boundary

Remove uVisor from mbed-os

Place "MBED_WEAK" for IAR-Toolchain before the type.

Added missing include.

Replace __attribute__((weak)) with MBED_WEAK

EFM32 Make PeripheralPins.c configuration tables weakly defined to be overridable. ...

See issue "https://github.com/ARMmbed/mbed-os/issues/7424#issuecomment-404233377"

EFM32: make peripherals conditional ...

* MCUs within a family like EFM32GG can omit some peripherals, e.g. EFM32GG230 doesn't have UART
* This commit adds a check to make them compilable, relevant mainly for custom boards

[Silicon Labs] Add bootloader support ...

* Make memory sections configurable in linker files
* Dynamically determine vector location in flash for NVIC relocation
* Advertise bootloader support in targets.json

Added mapping to BTN-labelled switches

Update to Gecko SDK 5.1.2 ...

Updating CMSIS device headers

uVisor: Standardize available legacy heap and stack ...

With the RTOS, the STACK_SIZE specified here is unrelated to the stack
size available for the main thread (that runs pre_main). Save memory by
reducing the stack size to a more reasonable amount.

On uVisor, HEAP_SIZE is both a minimum available and maximum available
heap size. The heap can't grow beyond the end of the heap into the
neighboring stack. On all uVisor-supported platforms, guarantee at least
0x6000 bytes of heap space. This increases the portability of uVisor
applications as the memory available for legacy heap allocations is
guaranteed. This helps to avoid out of memory errors on platforms that
were previously guaranteeing less memory.

EFM32GG: Fix GCC_ARM linker script ...

A copy paste error snuck into the uVisor related updates to the EFM32GG
linker script. Fix the error by replacing "m_data" with "RAM".

Fixes: 89641bc7e0ce "uVisor: Update K64F and EFM32GG linker scripts"

uVisor: Update K64F and EFM32GG linker scripts ...

This commit improves consistency between different platforms' linker
scripts. In particular, we use "__UVISOR_SRAM_START" instead of
"__UVISOR_BSS_START" as the uVisor BSS sections might be outside of the
SRAM (for example, when using a tightly-coupled memory).