Add TX-buffer for MarlinSerial

Similar to the current Arduino HardwareSerial
but with max. 256 byte buffer-size.

Deactivated by default.

The boards with AT90USB processor (USBCON) already use a TX-buffer.

MarlinSerial emergency-command parser (with M108)

Add an emergency-command parser to MarlinSerial's RX interrupt.

The parser tries to find and execute M108,M112,M410 before the commands disappear in the RX-buffer.

To avoid false positives for M117, comments and commands followed by filenames (M23, M28, M30, M32, M33) are filtered.

This enables Marlin to receive and react on the Emergency command at all times - regardless of whether the buffers are full or not. It remains to convince hosts to send the commands. To inform the hosts about the new feature a new entry in the M115-report was made. "`EMERGENCY_CODES:M112,M108,M410;`".

The parser is fast. It only ever needs two switch decisions and one assignment of the new state for every character.

One problem remains. If the host has sent an incomplete line before sending an emergency command the emergency command could be omitted when the parser is in `state_IGNORE`.
In that case the host should send "\ncommand\n"

Also introduces M108 to break the waiting for the heaters in M109, M190 and M303.

Rename `cancel_heatup` to `wait_for_heatup` to better see the purpose.

Fix quick homing, tweak MIN_Z_HEIGHT_FOR_HOMING

Move XYZ in print_xyz and DEBUG_POS to the front

Don't use axis_codes if a literal will do

Fix comment on Z raise for homing, save a few bytes

Don't do_probe_raise with MIN_Z_HEIGHT_FOR_HOMING

[LANGUAGE] Update Czech (filament change and info)

Change cancel_heatup to wait_for_heatup

Clean up, simplify and generalize the Allen-key-probe code.

Move and extend axis_unhomed test to deploy/stow_z_probe().
Move and extend position store/restore to deploy/stow_z_probe().

Now all kinds of probes can use the 'E' parameter in G29/M48.
Allen key probes can be used now for grid and 3-point levelling.

Deploying the Allen Key probe uses big moves in z direction.
Too dangerous for an unhomed z-axis.
Throw a compile time error when we try to configure an
Allen Key probe homing to z-min and having no other z-min-endstop.

The `PROBE_IS_TRIGGERED_WHEN_STOWED_TEST` is able to detect if a probe is
successfully deployed/stowed.
It was part of the Allen Key probes code only.
Now the function is generally available.

Currently this test is compulsory for Allen Key probes to not alter the used behaviour
If you want to add the test for an other type of probe simply add
```
#define PROBE_IS_TRIGGERED_WHEN_STOWED_TEST
```
to your config.

There was an hidden extra move after the scripts. This is configurable now.
Added the extra moves to the relevant configs.

Add a optional feedrate parameter to `do_blocking_move()` and its companions.

Allow the command queue to be cleared by commands, lcd menus

Make raise for probe deploy relative in homeaxis()

MBL typo

Make raise for probe deploy relative in homeaxis()
by setting `current_position[axis]` to zero later.

Introduce M108 cancel wait for heatup/cooldown of the hotend and bed

Additional patches for gcode_T position change

References to millimeters in code comments need an update

Remove wants_to_cool uninitialized warning

Remove wants_to_cool warning

Fix position adjustment with gcode_T and MBL