Misuse of FreeRTOS task notifications as semaphores without give/take API

[mincrmatt12]

Right now there seems to be race conditions in places where we wait for a task to do something because I've somehow failed to notice that FreeRTOS has a separate semaphore API for task notifications (i.e. for waiting on notification state >= 0) that would solve a significant number of problems.

Fixes required in:

• servicer (stm)
• serial (esp)
  • to grabber
  • to dupm
• matrix refresh (stm)

[mincrmatt12]

(apparently the FreeRTOS on the ESP8266 is too old to use them in esp-land, but the recent mutex should totally alleviate the problem) edit: this is apparently not true, I was being fooled by autocomplete (still the explicit mutexes completely alleviate the racing)