Adds spinner to change permissions button

Fixes active items being selectable

Enabled eslint

Toggle button text fix

Closes #343

Fix typo

See merge request !955

Change docs title to represent the edition

See merge request !961

[EE] Group members in project members view

See merge request !958

[ci skip] Update upgrade guide from GitLab CE to GitLab EE for 8.15

Following the steps from https://gitlab.com/gitlab-org/release-tools/blob/master/doc/release-candidates.md#creating-rc1.

See merge request !959

When the project has invitees, no group members were
returned due to a `user_id NOT IN (42, NULL)` query which
always returned [] since a `user_id` would be NULL, thus the condition
could never match.
Signed-off-by: Rémy Coutable <remy@rymai.me>

Closes #24122

Fix css lint

I merged [CE->EE](https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/953) with [failing css lint](https://gitlab.com/gitlab-org/gitlab-ee/builds/7216539), this is a fix.
It was caused by https://gitlab.com/gitlab-org/gitlab-ee/commit/d6d22a5dbd2ee04b59b2a80b3b6228575c3ea3ec on CE side.

@iamphill Please take a look if fixes are OK. If no, please send a separate MR to fix it.

See merge request !956