Both movable components now perform homing sequences transparently
whenever the logic layer invalidates the homingValid flag.
That reflects the fact, that the user may have moved the Idler or Selector
while trying to resolve a HW issue with un/loading filament.
Basic rules:
- Idler gets rehomed immediately and then moves into the target slot position
- Selector rehomes once it is possible - i.e. when filament load state
is AtPulley - then it immediately and spontanneously executes the homing
sequence and then returns to the desired state
Motivation:
- resolve startup issues (EEPROM says we have filament, but FINDA is not triggered)
- resolve accidental moves of Idler and/or Selector while
digging out stuck filament from the unit
- fix homing procedure for Idler and Selector
(homing now ends with a move to the Parking position)
- fix unit tests' startup conditions with regard to necessary
homing of Idler and Selector
TODO: still test_cut_filament fails for minor reasons
D.R.racer
3d-gussner