Update version to 8.12.0

Diff

https://gitlab.com/gitlab-org/gitlab-qa/compare/v8.11.0...cc2612ead6e4e5da8131c63cb9500e741c9128c2

Release notes:

New scenarios and scenario updates

• Pass in allow-local-requests variable for impor... (!1082 - merged)

Other changes (CI, backstage)

• Perform actions related to CI database only if ... (!1081 - merged)
• Use static descriptive names for gitlab instanc... (!1080 - merged)
• Add configurable Customer Portal URL for Licens... (!1048 - merged)

Checklist before merging:

• Diff link is up-to-date.
• Based on the diff, lib/gitlab/qa/version.rb is updated, according to SemVer.
• Release notes are accurate.

Checklist after merging:

• Update the release notes for the newly created tag.