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.
If Z_RAISE_BETWEEN_PROBINGS is null or undefined the probe is currently not raised by home_offset[Z_AXIS] and zprobe_zoffset.
But when different from 0 is.
If an undefined Z_RAISE_BETWEEN_PROBINGS expands to 0 (and it does) this is the solution.
A similar asymmetry exists with the newly introduced 'short-cut' in G28 - but its the rise before anything is probed - so should not make a difference.
`dock_sled()` is never called with offset parameter - remove it.
We move x only - so only that needs to be homed. Consequence is - we can home to z-min now with a sled probe!
Feedrates are set and restored in `do_blocking_move()`.
We already checked if the probe is deployed/stowed in deploy/stow_probe.
```
if (z_loc < _Z_RAISE_PROBE_DEPLOY_STOW + 5) z_loc = _Z_RAISE_PROBE_DEPLOY_STOW;
```
makes no sense - remove.
Now the raise is the same for deploy/stow -> move before the if.
Replace the if with a ternary.
Instead writing LOW/HIGH use the boolean `stow` we already have.
There is no reason for not using the sled probe in G29/M48 with 'E'.
It takes a while but works. (tested!)
Scott Lahteine