Refactor shared logic to base component

What does this MR do and why?

Related to #378677 (closed)

In &9056 we are migrating the user profile from HAML/jQuery to Vue. This is a large migration so we are splitting it up into many sections.

There are many contribution events that we will need to support. These are documented in https://docs.gitlab.com/ee/user/profile/contributions_calendar.html#user-contribution-events. As of now we have added support for approved, expired, joined, and left events. See !122676 (closed) for how every event will be implemented (not including this refactor). I am currently cherry-picking events from that MR into individual MRs to make them smaller and easier to review.

All event components use the contribution_event_base.vue component. Previously this base component was only responsible for rendering the user avatar and each individual event component was responsible for rendering the message. I realized that all of the events except pushed and private are going to follow the same message format. This means that we can abstract a lot of the message logic to contribution_event_base.vue. For the two events that do not follow this message format we can still allow them to use the default slot to render the message.

UX note: There is currently an incorrect bottom border in the tabs. This is due to a recent change in !118597 (merged). We will be removing the tabs and moving the navigation into the new sidebar in #389842. By removing the tabs we will be able to fix this bug and because this is behind a feature flag I am going to leave it as-is for now.

Screenshots or screen recordings

No visual changes, developer facing

How to set up and validate locally

1. Open the rails console
   • bin/rails console
2. Enable the profile_tabs_vue feature flag
   • Feature.enable(:profile_tabs_vue)
3. Go to a project and make note of the ID (shown on the overview page)
4. Run the following commands to create contribution events
   • user = User.find(1)
   • project = Project.find(<project ID from previous step>)
   • merge_request = MergeRequest.first
   • FactoryBot.create(:event, :expired, project: project, author: user)
   • FactoryBot.create(:event, :joined, project: project, author: user)
   • FactoryBot.create(:event, :left, project: project, author: user)
   • FactoryBot.create(:event, :approved, author: user, project: merge_request.project, target: merge_request)
5. Navigate to your profile

MR acceptance checklist

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