Unagii v3 vaults

[swunode]

To provide vault support for USDV-3CRV factory pools once USDV minting is out and factory contract deployed.

Vaults v3 will encompass of the following:

• Single vault that allows deposits and withdrawals similar to curve.
• Basically on deposits, you can opt to deposit in 1 stable, equally, or 4 different types of stables in different quantities.
• For withdrawals, users can choose to withdraw equally based on pool ratio, or withdraw in 1 single stable asset.
• Will support USDV, USDC, DAI, USDT deposits and withdrawals.
• On rewards harvesting, depending if Convex finance supports the pool or not, CVX + CRV will be sold back to best performing assets and re-compounded. VADER incentives will be burnt to USDV, then deposited back to the pool to compound.

All other v2 vaults will be deprecated by a fixed date, with liquidity migrated by "strategy switch" by team if not taken out, directly into USDV-3CRV pool.

Rationale: Consolidate liquidity into a single vault. Provide support to ecosystem project on vader. Less gas cost spent to maintain upkeep of vaults.