Make sure to only set the fan state once when extruders share a fan

Addressing #3743

Fix compilation error in Thermal Runaway debugging code

When setting the bed temp via M140/M190 if the thermistor does not read an increase of WATCH_BED_TEMP_INCREASE degrees by WATCH_BED_TEMP_PERIOD seconds then it will throw "Error:Heating failed, system stopped! Heater_ID: bed" and call the kill() function.

Conflicts:
	Marlin/Configuration_adv.h

As noted by @FalloutBe in #3519

・Add more "UL" suffix
・Restore removed "UL" suffix

Only measure and store filament width when E is going forward.

Following up on #3231

Fixes for #3189

Setting a temp is still missing

Adds the parameter U to M303. If U1 is included , it will use the
PID-values from the auto-tune.

Addition to #3140

Addressing #3085. If the target_temperature is set directly it never invokes or disables the timer set in `start_watching_heater`, so after _stopping a print_ or turning off _all heaters_ you could get a “Heating failed” error.

Apply `constrain`, `NOMORE`, `NOLESS` and `CRITICAL_SECTION` macros
wherever possible.

Based on #2860 - rebased for RCBugFix