GHO CCIP 1.5.1 Upgrade Eth<>Arb

[DhairyaSethi]

Goal

Upgrade Existing ETH & ARB token pools to CCIP 1.5.1 by deploying new token pools, migrating liquidity to them & completely deprecating existing token pools.
This AIP aims to achieve this by:

1. Accepting ownerships of:
   • new token pool
   • admin role for GHO token of CCIP TokenAdminRegistry
   • existing proxy pool (even though they'll be deprecated)
2. Migrating Liquidity between old & new token pools:
   • ETH (LockRelease type): move tokens to new pool & update currentBridged
   • ARB (BurnMint type): Mint tokens on new pool, transfer to old pool, and burn tokens from old pool - this is done to offboard old pool as a facilitator and enable the new pool to offRamp existing bridged supply. (note that a facilitator can only burn (offRamp) amount which it has itself minted)
3. Setup new token pool with rate limits of 300k capacity & 60 rate.
4. Update Stewards with the new token pools.

Notes:

• the proxy pattern used is vanilla OZ v5.1 transparent.
• sanity check no leftover tokens in existing eth token pool.
• we can upgrade the existing ETH pool to reset bridgedAmount as well, but it's not needed since we reset bridgeLimit.
• 1.5.1 TokenPools: CCIP 1.5.1 aave/ccip#20
• For 2.b: Since the existing burn mint type token pool does not have an explicit method to burn supply, a new permissioned method directBurn is introduced in DirectBurn on RemotePool aave/ccip#21

[MichaelMorami]

✅ The upgrade was fully reviewed and approved by Certora.