Move ext_rc_define_gf_group_structure

Move the function into define_gf_group().
define_gf_group() has a lot of settings that might cause
performance drop if skipped.

Imitate define_gf_group_structure()'s behavior which add
an extra overlay frame at the end of gf_group whenever
alt_ref is used.

After this change, we can feed the baseline decision through
webmrc and get the same result as baseline.

This CL is tested with city_cif.yuv using ffmpeg

BUG = b/345528565

Change-Id: Ib61f0a0a72251f8662fb4072e0cfd7f456a243b3
2 files changed