The real fix. PR #13568 was wrong.

Mostly from the L6470-oriented PR

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

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.

- The documentation is correct. The code was wrong.

* Add parser.seen for multiple parameters
* Fix M666, use !seen for report
* Synchronize on M204, M205

* Universal tool-change Z lift
* Add TOOLCHANGE_ZRAISE to example configs
* Park/unpark changes to example configs
* Implement DEBUG_DXC_MODE

* Clean up Temperature PID
* Improve EEPROM read/write/validate
* Group `SINGLENOZZLE` saved settings
* Group planner saved settings
* Group filament change saved settings
* Group skew saved settings
* Group `FWRETRACT` saved settings

- Move FWRETRACT to the planner
- Combine leveling, skew, etc. in a single modifier method
- Have kinematic and non-kinematic moves call one planner method