Previously `AsynchronousMediaCodecCallback.mediaCodecException` was
cleared when flushing completed. This behaviour was changed in
aeff51c507
so now the exception is not cleared.
The result after that commit was that we would **only** suppress/ignore
the expression if a flush was currently pending, and we would throw it
both before and after the flush. This doesn't really make sense, so this
commit changes the behaviour to also throw the exception during the
flush.
This commit also corrects the assertion in
`flush_withPendingError_resetsError` and deflakes it so that it
consistently passes. The previous version of this test, although the
assertion was incorrect, would often pass because the
`dequeueInputBuffer` call would happen while the `flush` was still
pending, so the exception was suppressed.
#minor-release
PiperOrigin-RevId: 540237228
248d1d99ec