stagefright: Move CodecCapabilities querying into MediaCodec

1. We cannot assume that codecs are OMX based
2. We still have a strange dependency where MediaCodec's
   create methods depend on MediaCodecList, which depends on
   MediaCodec's static method. This is to be untangled later.

Bug: 17108024
Change-Id: Idd619ee959627539a65f5f7da586108883dcb5f2