mpeg2ts: Handle bitstream shortfall errors gracefully

Implemented a numBitsLeft check before invoking the getBits method to
prevent a crash.

Added a check to unsigned integer variable in
parseProgramAssociationTable.

Bug: 155700550
Bug: 316035064

Test: ./mpeg2ts_extractor_fuzzer
Test: atest Mpeg2tsUnitTest
Test: atest CtsMediaExtractorTestCases

Change-Id: I1ef4c6bbb2916babf7528456f5c56d55a3e0da70