FE: Add a “Pending promotion” tab to the group and project, list the pending promotions there

We need to add Pending Promotion tab to display promotion request lists at Group and Project membership management pages (e.g. http://127.0.0.1:3000/groups/gitlab-org/-/group_members and http://127.0.0.1:3000/h5bp/html5-boilerplate/-/project_members).

Relevant BE issue to integrate with: #433173 (closed)

UI should match that in other tabs. Filtering and sorting is a nice-to-have at this stage.

This very page will later be used to display All SaaS pending promotions.

Draft UI:

Draft MR for integration PoC: !147249 (closed)

Draft implementation plan:

MR	status
Custom Component for the tab	workflowcomplete
Custom store or Apollo store	workflowcomplete
Pagination	workflowcomplete
Add the table with a proper UI	workflowcomplete
Remove the export button	workflowcomplete
Post refactoring (defined below)	workflowcomplete

Post refactoring issues (might need a separate maintenance issue):

• rename MEMBER_TYPES to tabs something
• refactor how group and project options (for CE and EE) are passed. Additional links: !148563 (diffs, comment 1856208988)
• consider using Apollo store (might wait till 4️⃣ [Iteration 4 - All SaaS API] Add Controls f... (&13331) is implemented and we start developing for ~"All SaaS" in 2️⃣ [Iteration 2 - SM API] Add Controls for Abi... (&13329 - closed)) moved to standalone issue: #464565