Add merkle tree hook to agent config

[tkporter]

Probably blocked on #2747 / associated work related to hook config / artifact / deploy management, where we'd like to generate the agent config based off the deployed hook address.

• Atm, V3 agents get the merkle tree hook by querying the Mailbox's requiredHook. We can't always assume that the Mailbox's requiredHook will be the merkle tree hook -- at best, this will result in incorrect behavior causing an agent to crash, at worst, this feels like a security problem
• Consider changing the config structure to be hooks.merkleTreeHook or something instead of just having merkleTreeHook alongside the mailbox, validator announce, etc. If we do this, then we should probably move the IGP in there too? Validator announce could be argued to be a hook too, but I don't feel strongly there tbh. I could see it also making sense to just keep merkleTreeHook alongside the mailbox though, just do whatever feels most natural & makes sense for the future
• Should make sure e2e tests still pass -- i.e. deploy tooling that creates the agent config json should include the merkleTreeHook

[tkporter]

2 days

[avious00]

agent portion of Kunal's merkle tree hook work