Change it so that:

  GroupMemberAllManager uses GroupMemberAll object
  ProjectMemberAllManager uses ProjectMemberAll object

Create GroupMemberAll and ProjectMemberAll objects that do not support
any Mixin type methods. Previously we were using GroupMember and
ProjectMember which support the `save()` and `delete()` methods but
those methods will not work with objects retrieved using the
`/members/all/` API calls.

`list()` API calls: [1]
  GET /groups/:id/members/all
  GET /projects/:id/members/all

`get()` API calls: [2]
  GET /groups/:id/members/all/:user_id
  GET /projects/:id/members/all/:user_id

Closes: #1825

[1] https://docs.gitlab.com/ee/api/members.html#list-all-members-of-a-group-or-project-including-inherited-and-invited-members
[2] https://docs.gitlab.com/ee/api/members.html#get-a-member-of-a-group-or-project-including-inherited-and-invited-members

The URL was missing a 'v' before the version number and thus the page
did 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/v3.0.0/faq.html#attribute-error-list
  add the 'v' --------------------------^

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.

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

The arguments `should_remove_source_branch` and
`merge_when_pipeline_succeeds` are optional arguments. We should not
be setting any default value for them.

https://docs.gitlab.com/ee/api/merge_requests.html#accept-mr

Closes: #1750

In the CLI we need to make sure the components put into the path
portion of the URL are url-encoded. Otherwise they will be interpreted
as part of the path. For example can specify the project ID as a path,
but in the URL it must be url-encoded or it doesn't work.

Also stop adding the components of the path as query parameters in the
URL.

Closes: #783
Closes: #1498

fix: change to `http_list` for some ProjectCommit methods

Fix the type-hints and use `http_list()` for the ProjectCommits methods:
   - diff()
   - merge_requests()
   - refs()

This will enable using the pagination support we have for lists.

Closes: #1805
Closes: #1231