Persist user_access authorizations

NOTE: This MR is built on top of Introduce user access authorizations (!116901 - merged).

What does this MR do and why?

This MR persists the authorization information through user_access keyword. This is necessary for the next optimization. Please see Persist GitLab agent's user access configuratio... (#389430 - closed) for more information.

A few notes:

• This feature is behind kas_user_access feature flag which is disabled by default. It's not exposed to end-users yet.
• See https://gitlab.com/gitlab-org/cluster-integration/gitlab-agent/-/blob/master/doc/kubernetes_user_access.md for the feature spec details.
• Related to Persist GitLab agent's user access configuratio... (#389430 - closed)

Screenshots or screen recordings

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How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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