feat: Hide private fields on hover depending on context

[Veykril]

Hides private fields as follows

Hover location	Definition location	Render private fields?
Workspace crate	Workspace crate	Yes
Workspace crate	External/library crate	No
External/library crate	Same external/library crate	Yes
External/library crate	Different external/library crate	No
Anywhere	Same crate as definition	Yes

[ChayimFriedman2]

FWIW I do find private fields useful but as long as it's configurable I don't object (even if it's off by default).

[Veykril]

I am curious about that thought, I think I was of the same opinion before but at this point I've kind of changed my mind. If its a private field in a dep I don't really see how it would be useful in the common case to see since it wont ever be possible for me to change that. And in the very rare case where it is interesting to then see one could always go to def. Hence this PR.