Enable addon provider fleet as experimental

[Danil-Grigorev]

What this PR does / why we need it:

This change introduces CAAPF as experimental feature in turtles, bringing automatic Fleet cluster management per CAPI cluster, and tight ClusterClass integration with ClusterGroups.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged): Fixes #

Special notes for your reviewer:

Checklist:

• [ ] squashed commits into logical changes
• [ ] includes documentation
• [ ] adds unit tests
• [x] adds or updates e2e tests