* Apply #pragma once in headers
* Adjust some thermistors formatting
* Misc cleanup and formatting

Always honor minimum period on stepper pulse generation, and fix timing calculations

Signed-off-by: etagle <ejtagle@hotmail.com>

Also simplify logic on all ARM-based interrupts. Now, it is REQUIRED to properly configure interrupt priority. USART should have highest priority, followed by Stepper, and then all others.

Followup to #9985

To reduce confusion over the current timer count vs. the compare (aka "top") value. Caution: this re-uses the function name, changing its meaning.