Implement AVR Platform

Fix compile error when UBL is enabled but there is no LCD Panel.

20x4 map integration.    Also some minor changes to the UBL Menu layout.     Both 20x4 LCD's and Graphical LCD panels should have similar functionality now.

Fixes #6445

All the changes to get the code into compliance with Marlin coding
standards made UBL sick.   This pretty much gets UBL back up and
running.

Especialy against stepper ISR.
This is even more important when a minimum pulse width is set,
increasing the runtime of a babystep.

To guarantee that the 5mS pulse from a BLTouch is recognized you need to
have the endstops.update() routine run twice in that 5mS period.

At 200 steps per mm, my system has problems  below a feedrate of 120 mm
per minute.

Two things were done to guarantee the two updates within 5mS:
1) In interrupt mode, a check was added to the temperature ISR.  If the
endstop interrupt flag/counter is active then it'll kick off the endstop
update routine every 1mS until the flag/counter is zero.  This
flag/counter is decremented by the temperature ISR AND by the stepper
ISR.

2) In poling mode, code was added to the stepper ISR that will make sure
the ISR runs about every 1.5mS.  The "extra" ISR runs only check the
endstops.  This was done by grabbing the intended ISR delay and, if it's
over 2.0mS, splitting the intended delay into multiple smaller delays.
The first delay can be up to 2.0mS, the next ones 1.5mS (as needed) and
the last no less than 0.5mS.

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BLTouch error state recovery

If BLTouch already active when deploying the probe then try to reset it
& clear the probe.

If that doesn't fix it then declare an error.

Also added BLTouch init routine to startup section

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.

Instead of waiting for a single long block, compare the complete block
buffer runtime for the long_move() check.