Honor the "Remember me" parameter for OAuth-based login

What does this MR do?

• Add a "Remember Me" button for OAuth-based login
• OAuth-based sessions should persist past a browser restart if "Remember Me" was checked

Are there points in the code the reviewer needs to double check?

• Nothing yet.

Screenshots (if relevant)

References

• Closes #18000 (closed)
• Corresponding EE MR: gitlab-ee!2175

Tasks

• Investigation
• Implementation
  • Pass the remember_me parameter through
  • Don't use inline javascript to change the remember_me parameter
  • SAML
  • Other OAuth providers
• Tests
  • Added
    • Get the OmniAuth flow working under an integration test
    • Add tests for all OAuth flows without remember me
    • Add tests for all flows with remember me
  • Tests seem to be dependent on gitlab.yml
  • Passing
• Follow-up
  • Manually recheck that this strategy works
  • Manually recheck that this strategy works with 2FA on
• Meta
  • CHANGELOG entry created
  • Branch has no merge conflicts with master
  • Squashed related commits together
  • Check for clean merge with EE
• Review
  • Backend Reviewer
  • Frontend Reviewer
  • Maintainer
• Wait for merge