Move comment formatting (in C) to prism from CRuby

[kddnewton]

So that it can potentially be shared with other implementations.

https://github.com/ruby/ruby/blob/9b8e5bb85dc4c84fc9a19ffc2c9c5f89c360eab8/prism_compile.c#L10743-L11285