[4.5.1] battery - fix BATTERY_NOT_PRESENT detection, detection logic change

[haslinghuis]

• backport of #13599

• battery - fix BATTERY_NOT_PRESENT detection, detection logic change

Detection logic is refactored - battery voltage delta is tested each 50ms, voltage is considered stable when difference of last 10 samples is smaller than 100mV This makes stable threshold more forgiving than #13350 (time for comparison is 50 instead of 500ms).

• battery - improve stable voltage detection

• voltageStablePrevFiltered every time delta is exceeded

• voltage within range is ANDed over 100ms periods

• voltage is stable if it was within range for 10 out of 11 periods

  • slowly changing voltage will update threshold, but voltage will be considered stable
  • 1 update/s (100mV/s) is tolerated

• battery - fuix typos, improve comments

[github-actions[bot]]

Do you want to test this code? You can flash it directly from Betaflight Configurator:

• Simply put #13623 (this pull request number) in the Select commit field of the Configurator firmware flasher tab (you need to Enable expert mode, Show release candidates and Development).

WARNING: It may be unstable. Use only for testing!