Implement AVR Platform

Addressing #6992 and #5851

* Change all direct changes of ubl.state.active to
  set_bed_leveling_enabled() which handles apply/unapply
  leveling to maintain current_position consistency.

Fix invalidation of UBL mesh to invalid unreachable
  mesh points as well (delta corners).

Fix UBL_DELTA unapply_leveling logic and when
it gets applied, including fade_height changes.

Add optional M114 D for detailed position information,
disabled from compilation by default (M114_DETAIL).

* UBL_DELTA raw and inline kinematics

* UBL planner fall through fix

* consistent variable names

* Cleanup orphaned code and whitespace changes.
Use _O2.

* compile warnings cleanup

* Remove redundant #ifdef condition

UBL on Delta's....     Should be close!    Should not affect any Cartesian printer.

Firmware was forgetting the z_fade_height in Planner, set by M420 Z<f>,
after each reset or loading settings from EEPROM. Added the float
z_fade_height to EEPROM-Storage, now remembers the value.

Work around for slicers producing buggy gcode.

Followup to #5840

Hopefully fixes Marlin #5481

The target here is to update the screens of graphical and char base
displays as fast as possible, without draining the planner buffer too much.

For that measure the time it takes to draw and transfer one
(partial) screen to the display. Build a max. value from that.
Because ther can be large differences, depending on how much the display
updates are interrupted, the max value is decreased by one ms/s. This way
it can shrink again.
On the other side we keep track on how much time it takes to empty the
planner buffer.
Now we draw the next (partial) display update only then, when we do not
drain the planner buffer to much. We draw only when the time in the
buffer is two times larger than a update takes, or the buffer is empty anyway.

When we have begun to draw a screen we do not wait until the next 100ms
time slot comes. We draw the next partial screen as fast as possible, but
give the system a chance to refill the buffers a bit.

When we see, during drawing a screen, the screen contend has changed,
we stop the current draw and begin to draw the new content from the top.

`block_buffer_runtime_us` is mangled in the planner and in the stepper-ISR.
So it needs to be volatile and interrupt protected.