Add nodoc filter to doc type methods

[spuun]

The doc generator is creating links to non-documented type. I tried to fix this in #14878, but it turned that it removed links to documented non-top-level types.

Instead, filters will now be applied in Doc::Type#ancestors, Doc::Type#included_modules and Doc::Type#extended_modules instead as it was already done in Doc::Type#subclasses.

Some specs to verify correct(?) behavior has been added.

Example of File.html.

Before:

After:

Fixes #9816, #12018

[straight-shoota]

I suppose it could be up for debate whether undocumented types should be entirely invisible. But there could be some value in at least mentioning their existence in some places?

So alternatively we could continue with the approach in #14878, just using must_be_included? as selection criterion instead of in?(types).

[spuun]

I suppose it could be up for debate whether undocumented types should be entirely invisible. But there could be some value in at least mentioning their existence in some places?

Hm, I guess. And the inherited methods for undocumented types too, I suppose?

So alternatively we could continue with the approach in #14878, just using must_be_included? as selection criterion instead of in?(types).

Maybe some conditions in _methods_inherited.html whether a text should be a link or not is enough?

[straight-shoota]

And the inherited methods for undocumented types too, I suppose?

Oh, that's a tricky one.
I guess not? When a method is defined in a nodoc namespace, it should be expected that the method is also supposed to be undocumented.

Maybe this is all fine then. Nodoc ancestors are supposed to be hidden and don't need to be mentioned anywhere in the API docs... 🤷

[straight-shoota]

This change was insufficient due to #15053 and got reverted in #15064