FOME uses unmaintained rusefi/ChibiOS branch

It looks like rusefi has started maintaining a new branch of ChibiOS, with recent developments primarily focused on [AT32 / Artery](https://www.arterychip.com/en/product/index.jsp?t=1737015512570) things, hacking at v20 to support rusefi things and backport some specific fixes from upstream. Additionally this branch is re-written against upstream at practically (or just before) the original branches fork.

The new branch is `rusefi/stable_20.3.x.rusefi_clean_history`, the old branch (one FOME uses) is `rusefi/stable_20.3.x.rusefi`.

Of note, some important changes are being missed, like:
- :exclamation: https://github.com/rusefi/ChibiOS/pull/52
- https://github.com/rusefi/rusefi/issues/4556
- https://github.com/FOME-Tech/fome-fw/issues/80
- _see FOME-Tech/ChibiOS PRs below break_
- :exclamation: https://github.com/rusefi/ChibiOS/pull/47
- _[ChibiOS #1278 STM32 HAL UART ISR flaw](https://sourceforge.net/p/chibios/bugs/1278/)_
- ChibiOS fix (v20): https://github.com/ChibiOS/ChibiOS/commit/29bedb342aa6816144306f30559dcee39ef4f5fc
- rusefi fix: https://github.com/rusefi/ChibiOS/commit/a173d119f1c43ce0adcba454046098817bcf71d7
- _STM32: USARTv1: improve baud rate calculation accuracity_
- ChibiOS fix (v21): https://github.com/rusefi/ChibiOS/commit/26f74fcbd355e0417655d4659821291a29275005
- rusefi fix: https://github.com/rusefi/ChibiOS/commit/adeb3c34cf5990f51a6b90eac52ed58f39d344ff
- :exclamation: https://github.com/rusefi/ChibiOS/commit/b3ae9ee85235abb9ef978660a731a60c853c7ef2
- :question: https://github.com/rusefi/ChibiOS/pull/42
- _Simplified FatFS bindings. Removed MMCSD experiment files._ / MMC Mutual Exclusion support
- ChibiOS fix (vNext): https://github.com/ChibiOS/ChibiOS/compare/2d9ad10b7ac9bd82434b43d76d0102459fb01259...81475ef61eb1651178e5ea26a752dd67686d9fab
- rusefi fix: https://github.com/rusefi/ChibiOS/commit/f869830718008ae7bc7c0f07594ce2a0fdfd1d14
- rusefi fix: https://github.com/rusefi/ChibiOS/commit/ad80e276ad411c23ce372aa31106b9c9fca259a1
- rusefi fix: https://github.com/rusefi/ChibiOS/commit/1e252e5d9f38986f39458dc66255a5c61bdde70a

----

- https://github.com/FOME-Tech/ChibiOS/pull/4
- https://github.com/FOME-Tech/ChibiOS/pull/5