4626 Vault for LSTs

[OisinKyne]

🎯 Problem to be solved

We need an address that accepts eth/weth, and mints an LST. It should track contributors and be able to unwind/exit.

🛠️ Proposed solution

Investigate 4636 implementations and make a PoC vault implementation.

• Approved design doc: link

🧪 Tests

👐 Additional acceptance criteria

❌ Out of Scope