Add Secondary Event Source / Better High Availability

[bonedaddy]

At the moment a highly available deployment of circuit-breaker would be running multiple instances of block-listener and contract-watcher services, each using the same RPC provider.

The best way to improve this would be to have multiple instances of block-listener and contract-watcher, each using a different RPC provider, or perhaps leveraging blocknative. That being said it would still be advisable to have multiple instances of the block-listener and contract-watcher services as this prevents issues with one host causing an outage of the circuit breaker.

Tagged as low-medium as it does not appear to be strictly necessary for correct operation.