Co-authored-by: Scott Lahteine <thinkyhead@users.noreply.github.com>

* Mitigate stepper timeout

* Add CHAMBER PWM code

* Structured thermistor tables

* Fix reversed sensor ranges

* Prevent temps outside sensor range

Co-Authored-By: AbdullahGheith <abdullahgheith@users.noreply.github.com>

Saves 128 bytes in testing with `mftest mega 1 -y`

And change verbiage to not refer to "Emergency Stop."

Co-Authored-By: Tim Moore <tim.moore@lightbend.com>
Co-Authored-By: AnHardt <github@kitelab.de>

- Send notifications to ExtUI for M0/M1

- wait_for_user can be non-volatile (not changed by interrupt)
  C / C++ compilers don't optimize away reads of non-volatile variables when a function call is used between accesses, because *any* variable could be changed by the function call. Since `wait_for_user` can't be changed without a function call, it should be non-volatile so the compiler can optimize away cases where it is read more than once without an intervening function call.