Deprecate the PROBE command's exported value
`{printer.probe.last_z_result}`. This value effectively returns the
toolhead Z position when the probe triggers and user's then need to
adjust the result using the probe's configured z_offset.
Introduce a new `{printer.probe.last_probe_position}` as a
replacement. This replacement has an easier to understand behavior -
it states that the probe hardware estimates that if the toolhead is
commanded to last_probe_position.x, last_probe_position.y and descends
then the tip of the toolhead should first make contact at a Z height
of last_probe_position.z . That is, the new exported value already
takes into account the probe's configured xyz offsets.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
32a5f2b042