Plane 3.9.3beta release

This is the first beta release for the 3.9.3 firmware. This release
has the following changes over 3.9.2:

  • fixed error handling for corrupt RC input that could lead to a
    crash in unusual circumstances (I don’t believe this has actually caused any crashes, this was discovered during code review)

  • fixed a race condition in IOMCU event startup that could lead to
    the safety not being disabled on boot with BRD_SAFETYENABLE=0

  • ensure surface speed scaling covers full range of configured

  • added builds for new boards F35Lightning, omnibusf4v6, mRoX21-777

  • updated GPIO numbers on AUX pins on all boards to be consistent
    with docs

  • updated KakuteF7 UARTs and buzzer

  • added ESC sensor uart on OmnibusNanoV6

Happy flying!