The URL was using the version number in the readthedocs link, but that
does not exist.

Previously the URL for python-gitlab 3.0.0 was:
https://python-gitlab.readthedocs.io/en/3.0.0/faq.html#attribute-error-list

Which does not exist.

Change it to:
https://python-gitlab.readthedocs.io/en/stable/faq.html#attribute-error-list

See https://docs.gitlab.com/ee/api/group_access_tokens.html

chore: add `pprint()` and `pformat()` methods to RESTObject

This is useful in debugging and testing. As can easily print out the
values from an instance in a more human-readable form.

test: add logging to `tests/functional/conftest.py`

fix: remove custom URL encoding

I have found trying to debug issues in the functional tests can be
difficult. Especially when trying to figure out failures in the CI
running on Github.

Add logging to `tests/functional/conftest.py` to have a better
understanding of what is happening during a test run which is useful
when trying to troubleshoot issues in the CI.

We were using `str.replace()` calls to take care of URL encoding
issues.

Switch them to use our `utils._url_encode()` function which itself uses
`urllib.parse.quote()`

Closes: #1356

fix: remove default arguments for mergerequests.merge()