[FE][chore] Migrate Group/Project Members app from VueX to Apollo

Note: see #464565 (comment 2143242355) note below for doubts about ownership and urgency of this task.

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As we move towards the GQL API in 2️⃣ [Iteration 2 - SM API] Add Controls for Abi... (&13329 - closed) — we can move to Apollo store for the groups/projects Promotion Requests app.

The migration is not anticipated to happen soon and may be considered around iteration 3, though this is still uncertain.

The migration should only be pursued if there is a plan to introduce more Apollo, which itself would depend on transitioning from injected data to GraphQL. If these conditions are met, prepare for an extensive refactoring effort estimated at 8+ story points.