Fix Z-move to uninitialized position in SWITCHING_EXTRUDERS tool_change (no_move=true)

* Optimize target_extruder, ignore T with mixing
* Give G-code Tn parity with tool_change

* Move special characters to language.h
* Apply some naming standards
* Clean up menu item draw functions
* Rename some Temperature methods
* UI => ExtUI

Followup to #12413

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.

* 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

Followup to #12137

Fix a bug introduced in #9582

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

- Drop `pgm_read_*_near` and let headers choose.
- Define `USE_EXECUTE_COMMANDS_IMMEDIATE` as a conditional.
- Add `process_subcommands_now` for SRAM-based commands.

In reference to #12175