* Make ExtUI respect MAXTEMP limits
  - Temperatures are now clamped by MAXTEMP limits rather than arbitrary values.
* Speed up USB init, add status
  - Speed up USB initialization
  - Show status message if init failed
* Enable status messages for EXTENSIBLE_UI
* Adjust max limit to MAX_TEMP - 15
* Misc. tweaks to formatting, const, etc.

Followup to #12770

On some T-Rex 2+ machines the previous max step rate could lose steps....

- `pins_BIQU_B300_V1.0.h` defines pins for B300, as found in the BIQU Thunder 3D printer.
- `pins_BIQU_SKR_V1.1.h` defines pins for bigtree/BIQU SKR V1.1 motherboard.

Implement initial support for MKS Robin (STM32F103ZET6) board.
Custom build script is used to generate encrypted firmware compatible with original MSK Robin bootloader (i.e. safe firmware update from SD card and possibility to go back to original close-source firmware).

Remove obsolete workarounds in G33 for the now fixed zprobe_zoffset bug

Fix #12594