Embed fil_actors_interface code in forest

[hanabi1224]

          We could have a vote maybe. I prefer the interface in forest to 

1. avoid publishing fil_actor_* crates on every change.
2. avoid the shim(e.g. miner::SectorOnChainInfo) in the current fil_actors_interface which does not implement LotusJson or JsonSchema and we have to re-define a same one in forest

Originally posted by @hanabi1224 in #4286 (comment)

[LesnyRumcajs]

No opinion if we acknowledge that nobody else uses fil_actor_states outside of Forest (and its fil_actors_interface), and we don't intend anyone to use it in the future.

[aatifsyed]

I would love for more autogeneration with that codebase