Enable pooled C2BlockPool

C2PooledBlockPool supports allocate & recycle blocks.
Currently C2PooledBlockPool supports C2LinearAllocation only.

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

Bug: 72651719
Change-Id: I3948afecf492ef62860c9e8f18fc9243ddca78bd