boards: add holybro/kakuteh7

known issues:
- flash-based params does not work on H7 (due to ECC), so params are on
  SD card. The last flash sector is still reserved however.
- output channel 6 does not support DShot (the implementation does not
  handle channel gaps)
- flashing of the 2. flash bank is much slower (around 3x), than the 1.
  bank for some unknown reason.
- after the BL jumps to the app, there's several seconds passing until
  stm32_boardinitialize() is called.

.github/workflows/compile_nuttx.yml

@@ -33,6 +33,7 @@ jobs:
           holybro_can-gps-v1,
           holybro_durandal-v1,
           holybro_kakutef7,
+          holybro_kakuteh7,
           holybro_pix32v5,
           matek_h743-slim,
           modalai_fc-v1,