Allow multiple JSON RPC providers for the same network

[tilacog]

Currently, networks can only be configured by having a single JSON RPC provider.

For robustness, it would be ideal if we could configure multiple providers for the same network, just like graph-node does.

Therefore, if the Block Oracle would try the following provider in case the previous was unresponsive or behaved in an unpredictable manner.

[matthewdarwin]

I think this is not a high priority. Indexers can run proxyd and have multiple providers behind that.

That is graph-node->proxyd->rpc

[azf20]

@matthewdarwin this is an issue for the block-oracle repository. I agree that the block oracle could leverage a proxy as you describe, @fordN @tilacog can you provide any more recent context on this requirement?