Avoid copying entire pbi->mb before decode_tile.
Avoid copying entire pbi->mb before decode_tile.

pbi->mb is a big struct (47.3 KB in 64-bit build). To fix the mismatch
fixed in https://aomedia-review.googlesource.com/c/aom/+/59091, only
the current_qindex field in td->xd needs to be reset in
tile_worker_hook_init before each decode_tile call. This is specified in
Section 5.11.1 of the spec. To match Section 5.11.2 of the spec, also
reset the delta_lf related fields (delta_lf_from_base and delta_lf) by
calling the new av1_reset_loop_filter_delta function.

Change the single-threaded decode_tiles function to match the
multithreaded counterparts.

BUG=aomedia:1918

Change-Id: I17a1fedd6d596fb01555d861ff44586dd1dcee43

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom