AI Impact - RCA: [FE] Add RCA usage tile

Overview

Once AI Impact - [BE] Root cause analysis users - Co... (#486523 - closed) • Amr Taha • 18.0 will be completed we need to add the Root cause analysis of unique users tile to AI Impact.

Problem to solve

Proposal

1. UI Spec:
   • Tile title: Duo RCA: Unique users
   • Value: percentage , calculated via rootCauseAnalysisUsers / duoAssignedUsersCount
   • ℹ️️ rootCauseAnalysisUsers out of duoAssignedUsersCount GitLab Duo users interacted with Duo Root cause analysis in the last 30 days.
   • See docs - https://docs.gitlab.com/ee/user/gitlab_duo/use_cases.html#root-cause-analysis-use-cases
2. Add the last 30 days as the titleIcon field.
3. Objective: This metric indicates how often Duo RCA used by users, reflecting the adoption rate indicate if users find it useful and effective for their tasks.
4. Definition: The % of unique users who used Root Cause Analysis least once in last 30 days.
5. backend source - AI Impact - [BE] Root cause analysis users - Co... (#486523 - closed)

• This should be behinds FF until the adoption Dashboard - https://gitlab.com/gitlab-org/gitlab/-/issues/505532+ UX Design is ready.