Add a test for the initial policy and average policy for CFR and CFR-BR.
Add a test for the initial policy and average policy for CFR and CFR-BR.

PiperOrigin-RevId: 270254279
Change-Id: I378077ad360f9caf74bdcc0b42a4a7d197beba87

deepmind/open_spiel,deepmind/open_spiel,deepmind/open_spiel,deepmind/open_spiel,deepmind/open_spiel,deepmind/open_spiel