Optic checks were being propagated unconditionally in loops,
causing nearly every node in an optic network to be checked every
time.
This restores behavior to the original intended behavior of
propagating forward changes on next tick, but stopping at points
where state quiesces.
Unfortunately beam obstruction sensing has been working
instantaneously because of this bug, and that will revert to the
original intended behavior of having those picked up only on
random checks, which may cause regressions in some builds.
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