* Remove redundant SITL ioPortDef_s array definition
* Minor cleanup of some logic where SIMULATOR is in ./src/main
* Updated based on feedback from @ledvinap
* Reducing scope as per @ledvinap
* Fix unit test
* Removing serial port avoidance in totality (unused).
TODO: Remove PWM/PPM radio inputs in another PR.
* Adding common source location in ./src/platform
To enable the continued clean up of multiple files still in ./src/main/driver (more PRs to follow) that are specifically for AT32, APM32 and STM32
Source will be moved to MCU_COMMON_SRC where it is specifically for that MCU (or variant). The test will be to ensure no files in the MCU_EXCLUDES for SITL.
* Use of +=
