RCA - License checks / availability

Problem

Not all organizations will want to allow access to the feature.

Proposal

• We would like for users to have an option to enable/disable the RCA feature (See https://gitlab.com/gitlab-org/gitlab/-/issues/444274#note_1898654381)
• RCA should be available for only Gitlab Ultimate customers with Gitlab Duo Enterprise
• RCA should be available on .com, dedicated and self-managed

Moved requirements

*We need to create an AI Gateway end point (See #441681 (comment 1881920961)) (captured in #459940 (closed))

• We also need additional gating for the RCA button on the job logs page.