Stabilize beacon temperature before BEACON_CALIBRATE measures Z offset

[cuiviemen]

The BEACON_CALIBRATE measures the z offset too soon after the MANUAL_PROBE is ACCEPTed by user. This leads to significant (IMO) offset in beacon temperature during final measurement.
To make the measurement more stable I propose:
Measurement is expected to be done when HW is in desired conditions - probe is at expected location (x,y,z) like center of the bed and the environment is properly set (bed, chamber temperatures) to its printing conditions. This is expected to be done on user side - DOC improvement?
User starts BEACON_CALIBRATE.
Beacon stores its temperature and z position.
User performs MANUAL_PROBE and ACCEPTs the value.
Beacon moves away (to initial z position).
Beacon waits for its temperature to stabilize (within certain range) onto the initial temperature.
Beacon performs the final measurement.

This way (mainly waiting on that initial temperature) we should have much more exact measurement to be stored.