The main interface documentation hasn't been updated substantially
since 2017 and is missing notes for many of its current features and
requirements.
Also change the recommendation for implementors from BasePlayer to
SimpleBasePlayer to ensure new classes are more likely to cover all
of the interface requirements.
#minor-release
PiperOrigin-RevId: 534027117
(cherry picked from commit d75e24a713dd8648ff775c6d29be6db30a7d31d9)
