feat(superchain): enable local testing

[edobry]

Description

This PR modifies the superchain configuration initialization logic to replace the PublicRPC endpoints not only in CI but also when running validation tests locally, as many of them require access to an L1 archive node in order to function properly. The previously-hardcoded URLs are extracted to test_rpc config values next to the existing public_rpc values they override.

This change required a modification to the proxyd-l1-ci IP whitelists to whitelist internal Tailnet IPs.

Additional Context

See a discussion of the issue here.

The initial PR whitelisting Tailnet IPs was misconfigured, but then fixed in this followup PR.

[bitwiseguy]

I think this could be a great improvement, but as it stands its not obvious why failures occur if trying to run validations locally without being connected to tailscale exit nodes. Forcing external users to "read the docs" to troubleshoot validations that previously worked is likely to cause friction. So I think it hurts the devx right now.

If we're going to merge this work, I think we should lift the L1 client connection so that we only attempt that once, instead of inside each validation. If the connection is successful, we pass that client connection to each underlying validation that needs it. If the connection fails (due to no tailscale connection), we should give a clear error message upfront (without running the full validation suite) about what to try (i.e. replace the rpcUrl in the relevant areas, and the url must be to an L1 archive node), and/or default/fallback to the current public full node urls