SDK / exoplayer

This is one step toward following the google3's test naming convention.
See go/java-testing/getting_started#basic-test-template for details
why prefix test isn't necessary.

This CL is generated by following command
$ find -name '*Test.java' | xargs -I{} sed -i 's/^\ \ public\ void\ test\([A-Z]\)\(.*\)$/  public void \L\1\E\2/' {}

and then manually modified following tests where test method names conflict with test target.
- VorbisUtilTest
- VorbisReaderTest
- UtilTest
- DownloadManagerDashTest
- DefaultOggSeekerTest
- OggPageHeaderTest
- HlsMasterPlaylistParserTest

PiperOrigin-RevId: 298074653