IMF: Factor out OnceResultReceiver to fix TextBoundsInfoResultReceiver

Fixes an issue with TextBoundsInfoResultReceiver, where any Executor
that does not run the Runnable directly crashes, because the mConsumer
is cleared before it is run. Also avoids calling into the executor
with internal locks held.

Bug: 265457058
Test: atest InputConnectionEndToEndTest
Change-Id: I4b229494fb2451135ae1075272f04d865a9b509e