* Add APM32F4 driver libraries and USB middleware
* Add the APM32F405 and APM32F407 target files
* Add APM32 startup files
* Add APM32F4 linker files
* Add APM32F4.mk
* Add APM32 driver files
* Add APM32F40X MCU type
* Sync with the Betaflight master branch and modify the driver directory structure
* Implement CLI on the APM32
* Implement ADC on the APM32
* Implement config streamer on the APM32
* Implement I2C on the APM32
* Implement SPI on the APM32
* Implement DSHOT on the APM32
* Implement transponder ir on the APM32
* Implement serial uart on the APM32
* Implement MCO on the APM32
* Implement DWT on the APM32
* Update the init.c file, adding APM32 MCO configuration
* Remove all duplicated APM32 driver files and retaining only the APM32 LIB directory
* Create APM32F4.mk
* Add linker files for APM32F405 and APM32F407
* Add startup and library config files for APM32F405 and APM32F407
* Add target files for APM32F405 and APM32F407
* Add apm32 MCU driver files
* Add build configuration for APM32 MCU
* Implement config streamer on APM32
* Implement CLI on the APM32
* Implement ADC on the APM32
* Implement RCC on the APM32
* Implement MCO on the APM32
* Implement I2C on the APM32
* Implement SPI on the APM32
* Implement serial uart on the APM32
* Implement IO on the APM32
* Implement DMA on the APM32
* Implement DSHOT on the APM32
* Implement transponder ir on the APM32
* Update init.c
* Add the inclusion of the 'platform.h' file to the APM USB driver source file
* Merge bus SPI duplicate code from APM32 to STM32
* Update timer_apm32.c
* Merge motor duplicate code from APM32 to STM32
* Merge serial uart duplicate code from APM32 to STM32
* Update APM32F4.mk
* Update cli.c
* Update APM32F4.mk
* Remove the apm32_flash_f4_split.ld
* Associate the apm32 linker file with stm32_flash_f4_split.ld
Converting the universal target as well.
Simplified timer management some.
Added F722 support for good measuer.
Fixed SITL, tests.
Cleanup after rebase.
Added support for all timer consumers and F7.
Fixed 'USE_DMA_SPEC' for F3, some cleanups.
