* 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

In reference to #11000