Support the hyperlane validator agent in Hyperlane integration to allow testing multisig bridges

## Description

We currently support the hyperlane agent image which comes with a few binaries in it out of the box.
We should aim to support the validator agent to allow `n` of these to be spun up and sign mailbox roots.

This will require extensive investigation on how to configure the validator agents and have them sign and expose signatures for relayers to query and include in msg relays.

The current deployment code will also need to be adjusted to be more flexible for deploying merkle root multisig ISMs.

Start by investigating how the Hyperlane validator agent is configured and how the current deployment code handles agents and merkle root multisig ISMs. Confirm how multiple validator agents can sign mailbox roots and expose signatures for relayers to query and include in message relays. Done means multisig bridge testing can deploy the required validators and complete these relays.

Written by the indexing model from the issue text.