Align labs rpc and local rpc on the path at least

[OisinKyne]

Problem to be solved

I didn't want to have to modify code to point from the local rpc (running in the stack), to pointing at obol rpc. the problem is the paths to our L1 json rpc are different:

Labs: https://erpc.gcp.obol.tech////"
On host: http://obol.stack/rpc/mainnet/
In stack: http://erpc.erpc.svc.cluster.local:4000/

Proposed solution

This fixes some of the issues (erpc config was rpc not network. but its hard to get three different domains identical. We should decide what's worth changing towards. maybe something like:

Labs: https://erpc.gcp.obol.tech/rpc/mainnet
On host: http://obol.stack/rpc/mainnet
In stack: http://rpc.erpc.svc.cluster.local/rpc/mainnet

If so i have changes in obol-infrastructure, and obol-stack-front-end to make before this should be merged.