This replaces all the duplicated logic previously implemented in
FakeSampleStream and more closely follows the pattern of how
SampleStreams are used from real MediaPeriods.
Some tests needed adjustments because using real the SampleQueue
improved behaviour:
- Waiting for isLoading is only needed once even across period
boundaries because the real SampleQueue doesn't have the on/off
pattern.
- AnalyticsCollectorTest.playlistOperations() was wrongly asserting
that some pre-buffering events. The new version is more intuitively
correct we pre-buffer the second item during the initial loading
phase (thus period1seq1) and keep the buffer in the queue after
the removal operation.
PiperOrigin-RevId: 348440255
30ee29df1a