MPEG2TSExtractor: get duration by seeking to end

Prerequisites for this implementation (included in this commit):
* DataSources:
  + add kIsLocalFileSource flag
* AnotherPacketSource:
  + implement getEstimatedBufferDurationUs
* ATSParser:
  + expose Event SourceType
  + expose first pts

Test: adb shell am start -a android.intent.action.VIEW -n <video player activity> -d <local ts file>
Bug: 31964524
Change-Id: Ifcb6b3246cfa3748ee4d87ed09dbdf62e963a6e5