Changes only affect UBL.  Everything else is left alone.

Fix #12416

Better handling of `ENABLED(MIXING_EXTRUDER) && !MIXING_VIRTUAL_TOOLS > 1` -  to not fall through to the general case. Fix compiler warnings for `#elif EXTRUDERS < 2`.

When endstops/probe are enabled `ENDSTOP_NOISE_THRESHOLD` calls to `update` are required to properly re-sync endstops/probe status.

* Group status methods, share reset_status with Extensible UI
* Move common DOGM code to headers

Fix #12399

Did not compile without  `WATCH_HOTENDS || WATCH_THE_BED`.
Add condition to include "../../module/temperature.h".

See if this has any deleterious effect on motion planning by slicers that inser their own jerk and acceleration controls. The problem I see is that these settings can take effect on blocks already in the planner, and the only way around this would be to shadow these settings in planner blocks and use the shadowed settings in the planner.

* Encapsulate common LCD code in a singleton
* Depend more UBL code on UBL_DEVEL_DEBUGGING
  - Since most users don't need the debugging on at all times, this helps reduce the default build size for UBL by over 2K, a little closer to fitting on 128K boards.

* Make lcd_quick_feedback argument optional
* Add click_to_cancel option to wait_for_hotend/bed
* Have G26 use the active nozzle and wait_for_hotend/bed
* Use wait_for_release in UBL G29
* Add 'T' parameter to G26 for an initial tool-change

- Partially reverts #11900 and tries to solve #12336

Fix #12362

Followup to #12137

Undo #12345

In reference to https://github.com/MarlinFirmware/Marlin/pull/12098#issuecomment-436231690

* Followup to LCD_TIMEOUT_TO_STATUS=0
* Make continuous purge screen fit 20x4
* Unify purge message modes
* Preserve last-set pause header mode