Add and document (some of the) optional parameters that can be done
for a `project.merge_requests.get()`

Closes #1775

There is an optional `squash_option` parameter which can be used when
creating Projects and UserProjects.

Closes #1744

It is not yet available upstream.

chore: add get() methods for GetWithoutIdMixin based classes

Add the get() methods for the GetWithoutIdMixin based classes.

Update the tests/meta/test_ensure_type_hints.py tests to check to
ensure that the get methods are defined with the correct return type.

Fix pylint error "expression-not-assigned" and remove check from the
disabled list.

And I personally think it is much more readable now and is less lines
of code.

Initial pylint check is added. A LONG list of disabled checks is also
added. In the future we should work through the list and resolve the
errors or disable them on a more granular level.