CCodec: buffer handling refactoring

- Separated Flex/Array implementation and Input/Output interface.
- Moved wrapping/conversion into Codec2Buffer interface.
- Use Create{Linear|Graphic}Buffer where applicable.

Test: setprop debug.stagefright.ccodec yes
Test: stagefright -S -N c2.google.avc.decoder /sdcard/a.mp4
Test: stagefright -ao -N c2.google.aac.decoder /sdcard/a.mp4
Test: audioloop -N c2.google.aac.encoder -M audio/mp4a-latm
Test: screenrecord --codec-name c2.google.avc.encoder /sdcard/record.mp4
Test: screenrecord --persistent-surface --codec-name c2.google.avc.encoder /sdcard/record.mp4
Fixes: 72445205
Change-Id: I5d0e95b63770b96d22ca8fbb30d054696e58e808