armv8-m: GCC/ArmClang: Remove redundant constant pools

Description

Currently in Armv8-M GCC/ArmClang ports, constant pool is used to define literals needed for ldr instruction. However, those constant pools are defined with .align 4 which increases code size. Instead of defining the constant pool with .align 4, let the compiler hanlde the constant pool and the required alignment.

Benchmarking these changes using Cortex-M85 (Corstone-315) and blinky application in https://github.com/FreeRTOS/iot-reference-arm-corstone3xx/tree/main/applications/blinky shows a code size reduction of 72 bytes (GCC) and 56 bytes (ArmClang).

Additional info: Armv8-M IAR port doesn't use any constant pool. With these changes all three ports GCC/ArmClang/IAR are aligned.

Test Steps

Validated the changes using GCC and ArmClang and using blinky application in https://github.com/FreeRTOS/iot-reference-arm-corstone3xx/tree/main/applications/blinky and:

Cortex-M85 (Corstone-315)
Cortex-M55 (Corstone-300)

Still to validate:

Cortex-M23
Cortex-M33

Checklist:

[x] I have tested my changes. No regression in existing tests.
[ ] I have modified and/or added unit-tests to cover the code changes in this Pull Request.

Related Issue

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FreeRTOS / FreeRTOS-Kernel