external/libgav1: backport sequence header fixes | DO NOT MERGE

cl/289966078: Move initial_display_delay out of OperatingParamet
cl/290784565: Handle a change of sequence header parameters.
cl/291222461: Disallow change of sequence header during a frame.

Together these provide additional coverage for the previous subsampling
fix [1], additionally adding coverage for bitdepth changes mid-frame. As
a side effect they also prevent the file from b/147491764 from
progressing to the original point of failure [2].

[1] ce9b99c external/libgav1: backport prediction subsampling fix
[2] 22ec187 external/libgav1: backport prediction border extension fix

Bug: b/147491773,b/147491764
Change-Id: I3f949e17c12990fc313522d9b2633509ee4e59a2
Test: upstream test vectors, repro test cases
(cherry picked from commit 760fb0d6f0766ca38b19ef57f8f9229aaeccca07)
5 files changed