C2SoftDav1dDec: Fix performance issues in frame parallel multi-threading

- dav1d_get_picture() was called more than necessary and that
 was leading to some performance issues. This is now cleaned up
 and this exposed few issues in how hdr metadata was being signalled
 in the current implementation.

- The HDR metadata was not getting associated to the picture being
 returned and was instead associated to the picture that was decoded.
 In case of frame parallel design, these two aren't necessarily the
 same. This is now fixed by associating metadata to the appropriate
 picture.

- Set max_frame_delay to 4 instead of letting the decoder pick a
 value. This is done to ensure max_frame_delay remains same across
 different device configurations, irrespective of number of cores.

Bug: 315828433
Test: atest CtsMediaDecoderTestCases:VideoDecoderPerfTest#testPerf \
-- --module-arg CtsMediaDecoderTestCases:instrumentation-arg:\
codec-prefix:=c2.android.av1
Test: atest CtsMediaV2TestCases -- --module-arg CtsMediaV2TestCases:\
instrumentation-arg:codec-prefix:=c2.android.av1
(cherry picked from https://android-review.googlesource.com/q/commit:98d9a24012dc1fb7f912afe1a8da12e832287d1b)
Merged-In: Ic2b0e15fb9aab31d293edcdd641f446d59480ab6
Change-Id: Ic2b0e15fb9aab31d293edcdd641f446d59480ab6