[pylint] add lint rule for docstring rtype format

[tjprescott]

For docstrings, we should have a linter rule to ensure the correct format is used:

wrong:

:rtype: :class:`azure.core.credentials.AccessToken`

right:

:rtype: ~azure.core.credentials.AccessToken

Additionally, APIView for Python will not recognize the first format and will likely yield an error that the docstring and type hint types do not match.

This rule should appy for rtype, type, paramtype and raises

[lb-cake]

👋@lmazuel is this issue still up for grabs? I'm new to contributing to OSS and would like to give this one a go.

[tjprescott]

@lb-cake yes, this is certainly up for grabs!

[tjprescott]

I don't even know what I assigned @lmazuel in the first place.