MediaCodec CTS: Code refactoring Move code that is common across media codec tests to codec test base class Bug: 147573846 Test: atest android.mediav2.cts.CodecEncoderTest \ android.mediav2.cts.CodecDecoderTest Change-Id: I82850f5f2021155b2243adbd0f27532951f46a33 Merged-In: I82850f5f2021155b2243adbd0f27532951f46a33