If the MMU receives a command LoadFilament with a slot number SL we reject
the command to avoid moving the selector (effectively cutting the piece of filament present in FINDA).
That includes the scenario when the selector is standing at the very same slot SL, because the filament could be held by the printer (i.e. loaded in the nozzle).
There is one special case though - same slot AND filament load state == InSelector (it MUST NOT be anywhere farther)
This commit looks horribly complex, but the main idea is to have each of the logic::commands
report their terminal OK state in the same way. That allow for leveraging this very moment
to initiate the idle timeout.
Additionally, I wanted to hide the logic of idle mode detection, which resulted in moving the
top level logic from main.cpp into logic/idle_mode.cpp and a set of additional files to compile
in unit tests.
D.R.racer