[DOC] Update functon-container cross-references and fix incorrect types

[tsbinns]

Discussed partially in call with @larsoner & @wmvanvliet.

There is a See Also section of the docstrings where connectivity functions link to the connectivity containers they return, and the container classes like to the connectivity functions they are returned from. These references were not present everywhere, and I wanted to make them consistent.

However, I found there were existing references where functions were linking to classes they did not return, and classes were linking to functions they were not returned from. There were also cases where the types of container classes returned in connectivity function docstrings were wrong.

There is also an inconsistency where the Connectivity class is sometimes used as an indicator of the generic BaseConnectivity class, and sometimes used to refer to the Connectivity class specifically. Just thought this could be a potential point of confusion. E.g. Connectivity is listed as the sole accepted class type in plot_connectivity_circle when anything inheriting from BaseConnectivity is allowed.
In this case I didn't change anything because I wasn't sure if others consider it problematic.

[tsbinns]

Were also some cases where noqa tags could be removed from docstrings thanks to the longer line lengths.

[larsoner]

@wmvanvliet I was confused why your approval didn't satisfy the merge requirements then I realized you didn't have write permissions on this repo. Now you're an admin 🚀

In it goes, thanks @tsbinns !