Enable Arduino Nano 33 BLE (#55) ...

* Add upload target for Arduino Nano 33 BLE, fix linker script preprocessing, add option for USB serial by default

* astyle error

* Use HINTS instead of PATHS so that the Arduino dir is searched first

* Enable OpenOCD and PyOCD for Nano 33 BLE in SWD mode

* Fix missing dependency for USB tests on Windows

* Add RAM defines for nrf52840

* Fix mbed-storage-kv-config depending on SD card library even if said library was not enabled

* Update dsrdtr value

* No longer need to modify linker script now that we aren't using whole-archive!

* Add OPENOCD_ADAPTER_SERIAL

* Add handling for cmsis dap

* Fix typo

* Fix weak symbol issue causing Bluetooth to not work.  In this case, the weak implementation can simply be removed, because there's no legitimate case where it is used.

Oops revert accidental linker script change

Convert mbed-ble to STATIC

GPIO: Use uintptr_t for gpio_irq_api context ...

The HAL gpio_irq_api stores object IDs, which serve as a form of context
for the dispatch of the interrupt handler in the drivers level
InterruptIn Class. The way this is achieved is that the InterruptIn
Class casts its address to uint32_t, which is stored as the ID.
This results in compilation failure when the size of an object pointer
is greater than uint32_t, for example when building on a PC for unit
testing.

In order to allow Unit Testing of the InterruptIn Class, we replace the
use of uint32_t with uintptr_t (type capable of holding a pointer),
which allows portability and expresses intentions more clearly.
In aid of this latter goal, we also replace the use of the name "id"
with "context", to improve clarity - these are addresses of the context
related to that callback.

HAL: Remove duplication in TARGET_NRF52 gpio_api

nRF52: GPIO: Assert that init succeeds

Update UART pin names & add MBED_CONF_TARGET_STDIO_UART overrides

Add standard pin-names validation script & tests

EP_ATLAS: Remove requirement for USB library if not required ...

Move inclusion of USB header file within the existing
conditional pre-processor directive so the USB library
is not required if USB stdio console is disable

CMake: Fix EP_ATLAS build ...

Enable Onboard TELIT ME310 driver only when cellular library is included.

This allows us to remove the cellular library as a requirement

to build applications that do not require it (i.e Blinky).

Add subtarget_init files to cmake

Fix astyle issues

Add default app start and size limitations ...

This commit introduces a default application start address (`0x1000`) and size limitation (`0xDF000`) to accomodate the Nordic USB bootloader.

The bootloader consists of a master boot record in flash from address `0x0` to `0x1000` and the actual bootloader application starting at `0xE0000` to the end of flash (`0x100000`). The bootloader enables firmware updates over USB using nRF Connect for Desktop.

More documentation regarding the open bootloader can be found here: https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.0.2/ble_sdk_app_open_bootloader.html

Add option to use USBSerial for stdio console ...

This commit introduces an option, `ep-atlas.enable-usb-stdio-console`, that will retarget the Mbed stdio console handle to a USBSerial instance if enabled.

Please note that if your application uses USB, it will conflict with this option. You should disable this option and implement a composite USB device in your application if you require stdio over USB.

This option is disabled by default so it will not cause issues with existing user code.

Configure internal regulators at startup ...

This commit introduces an implementation of the `subtarget_sdk_init` startup hook (called during `mbed_sdk_init`) that configures the internal regulators of the nRF52840.

The configuration sets up the internal regulator to output 3.3V. If this is not done, the default system voltage may be too low for the on-board indicator LEDs to conduct (ie: system voltage is lower than LED forward voltage).

Introduce `subtarget_sdk_init` startup hook. ...

The `mbed_sdk_init` startup hook is implemented at the NRF52-series level and so is unavailable for override. This commit adds an additional startup hook for NRF52 subtargets to perform any other startup initialization required.

CMake: clean up code comments after refactor

CMake: Refactor all Nordic 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.

nRF52: properly clean pwm structures on deinit()

Arduino_NANO33BLE: don't define Arduino pins if compiling in Arduino core

NRF52840: 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 Nordic targets

MCU_NRF52832: use two-region memory layout (stack + heap) to support MicroLib ...

MicroLib is the lightweight C lib for the Arm toolchain and
used as the default C lib on bare metal builds with the Arm
toolchain. It requires two separate memory regions for stack
and heap.

The change is based on nRF52840.sct.

Merge pull request #13691 from jrobeson/drop-nordic-sdk11 ...

Remove unused Nordic TARGET_SDK_11

CMake: Use relative paths to list source files and directories ...

The absolute path is still required for listing linker
files as they are referenced from a function in the top
level CMake input source file.

CMake nrf52480: fix startup/linker inclusion

CMake: add mbed-os and mbed-baremetal targets ...

mbed-os consists of mbed-core and mbed-rtos
mbed-baremetal consists of mbed-core

The main change is for mbed-core. Changing from object library to be interface. This way it allows us to do the above to have 2 main targets for users to use.

This should be backward compatible change as mbed-os target we used contains the same files/options as previously set.

CMake: Rename CMake targets ...

* mbed-os renamed mbed-core
* mbed-os-<COMPONENT> renamed mbed-<COMPONENT>

CMake: replace usage of the mbed_add_cmake_directory_if_labels() function (#13754) ...

Directories that start with special prefixes (TARGET_, FEATURE_, COMPONENT_)  are added to the build based on Mbed target configuration from targets.json instead of calling utility function mbed_add_cmake_directory_if_labels().

CMake: Fix NRF52840_DK build failure ...

* Remove duplicated ARM toolchain directory
* Link with archived cryptocell 310 libraries instead
  of adding them as source files
* Provide default MBED_BOOT_STACK_SIZE definition
  in scatter file as is done for GCC_ARM linker file