Port prototype rbi generation to prism

[Earlopain]

Apart from porting to prism, this also does the following:

1. Remove variable tracking for type_of0.
   It contains AST::TypeParam but checked for inclusion of a Symbol. There's no difference in the output even when this is fixed, so I just removed it entirely
2. Have the parse method return declarations, make it a class method.
   Just more convenient with the new structure. Eventually rb prototype will do this as well
3. Allow to use it on jruby/truffleruby.
4. Split comment parsing from comment processing in the helper.
   In rbi the comments now come from a plain parse. When prototype rb uses prism as well, parse_comments can be removed (as well as most of the other helper methods there)

I tested this against code samples from https://github.com/Shopify/tapioca/blob/d029cc9c3f76865f61fdbaff68d75e18a0014764/spec/tapioca/gem/pipeline_spec.rb
The output is largely the same, and improved in some areas. For example, type_member with no paren is no longer considered an untyped constant. Previously that was only the case for type_member() or when an argument was passed like type_member(:out).

For #348

[Earlopain]

cc @eregon