codec2: list c2.* components in MediaCodecList

- Set proper media type for component interface and read them in
  CCodec instead of current hack.
- Define debug.stagefright.omx_default_rank to override default OMX.*
  rank value (currently set to be preferred over c2.*)
- Move MediaCodec::CreateByType logic from ACodec to MediaCodec.

Test: am instrument -e size small -w 'android.media.cts/android.support.test.runner.AndroidJUnitRunner'
Test: setprop debug.stagefright.ccodec yes
Test: killall mediaserver
Test: cts-tradefed run cts -m CtsMediaTestCases -t android.media.cts.MediaCodecListTest
Change-Id: I55bd10d2d8c65867eae654e5bd64ef545689e699