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.

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.

The same default value is provided in the GCC_ARM linker file.

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

* Update all scatterfiles to define MBED_RAM_START and MBED_RAM_SIZE.  These
get defined in mbed_lib.json when building with a SoftDevice but were missing
when no SoftDevice is brought in.
* Remove SDK 14.2 SoftDevice files.
* Add missing header file to qspi_api.c.

- Adjust memory for SoftDevice
    - Enable PRIO=5 for interrupt priority check
    - Change NRF_SD_BLE_API_VERSION to 6
    - Add handle and buffer for advertising and scanning
    - Remove guard for phy update
    - Change scatter files and mbed_lib.json for PR #8607

When the SoftDevice (SD) is enabled we need to set the app_offset
to 0x26000 to make room for the SoftDevice.  If we let the build
tools self-manage this, MBED_APP_START is coming out at 0x25000
which is not correct for the Nordic 15.0 SDK.

The app_offset value is translated to MBED_APP_START by the build
infrastructure.  We were hard coding MBED_APP_START in the scatter
and ld files as a temporary measure while testing.  This now sets
it properly if the SD is being brought in.

- Use new NRFX header file
- Fix nRF52832 linker script/ld files (hardcoded addresses for now)
- Temporarily remove DEVICE_TRNG for nRF52832 (which broke the build)
- Improve serial_putc() fix so we don't rely on "extra" functions

--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

NRF52: add a separate .nvictable section and allow .noinit to be used…

The nrf section features has different implementations for each compilers supported by mbed-os. The header guard was ruling out compiler other than GCC by checking if __GNUC__ is defined. This check is not applicable on mbed os as the ARM compiler compile sources with gnu compatibility.

This patch makes sure that the right implementation is selected for the right compiler . The previous patch has been reverted as it is not reliable.

* Add NRF_SD_BLE_API_VERSION=5 macro to MCU_NRF52832 target
* Added initial Softdevice v5 API support for nRF5XPalGattClient.cpp
* Added initial Softdevice v5 API support for nRF5xGap.h
* Added initial Softdevice v5 API support for nRF5xGattServer.cpp
* Make sure the ah() hash function used by the security manager is declared with C linkage
* Removed 'ARM porting pending' checks in Nordic SDK
* Added BLE configuration to mbed_lib.json for NRF52x targets
* Migrated APIs and events model for Nordic SDK14.2 & SD API v5 in btle.cpp; adopted polling dispatch model
* Migrated APIs and events model for Nordic SDK14.2 & SD API v5 in nRF5xn.cpp
* Migrated APIs and events model for Nordic SDK14.2 & SD API v5 in nRF5xGap.cpp
* Added const qualifier to hwCallbacks's p_ble_evt parameter in nRF5xGattServer
* Add workaround to enable Radio Notification module from Nordic SDK
  * Disabled SWI1 interrupt manually from SWI driver module
    * Added missing include directive for "nrf_nvic.h" in ble_radio_notification.c
* Set correct number of custom UUIDs
* Adjust Softdevice RAM requirements for NRF52832/S132
  * RAM settings for the application were adjusted as follow:
    * Start: 0x20003800
    * Size: 0xC800
* Adjust Softdevice RAM requirements for NRF52840/S140
  * RAM settings for the application were adjusted as follow:
    * Start: 0x20003700 (was 0x20003000)
    * Size: 0xC900
* Added 3dBm as a permitted TX Power value for NRF52832
* Fix address type recovery in GAP
* Return min non-connectable adv interval compatible with infrastrcture's expectations
* Moved BLE driver from TARGET_SDK_14_2/FEATURE_BLE to TARGET_SDK_14_2/TARGET_SOFTDEVICE_COMMON/ble

Various bug fixes:

 * Moved SPIM3 location in vector table based on new location in SDK 14.2.
 * Updated vector table entries and size in startup code and linker scripts.
 * Added missing vector table RAM section to IAR linker script.

Ability to swap SoftDevices using the mbed configuration system.

For example, build NRF52840_DK without SoftDevice:

    "target_overrides": {
        "*": {
            "target.MERGE_SOFT_DEVICE": false,
            "target.extra_labels_remove": ["SOFTDEVICE_COMMON", "SOFTDEVICE_S140"],
            "target.extra_labels_add": ["SOFTDEVICE_NONE"]
        }
    }

Pinned down vector table to beginningn of RAM.

Flash and RAM offsets have been modified to fit new SoftDevice