codec2: enc stat: add local params

- C2_PARAMKEY_AVERAGE_QP
- C2_PARAMKEY_PICTURE_TYPE

those are not configurable param and
it could be informed from codec component.

Bug: 222205463
Test: atest android.media.codec.cts.VideoEncodingStatisticsTest

Signed-off-by: Taehwan Kim <t_h.kim@samsung.com>
Change-Id: I6269cfc39122b940f9aeb7282913dbeb6b58ea4b