Leave project/group from access granted email

What does this MR do?

CE: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/27892

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/59421

Remove yourself from a group or project with one click

Note, the 2nd last commit is a cherry-pick of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/11864 so I didn't have to write code twice.

• Add leave link to access_granted email

• Handle leave in query string by clicking the leave link automagically

  • If no leave link, flash error

Follow-up issues

https://gitlab.com/gitlab-org/gitlab-ce/issues/61169

https://gitlab.com/gitlab-org/gitlab-ce/issues/61170

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team