feat(actions): add GH self-hosted runner for tests requiring network syncs

[gustavovalverde]

Motivation

Using self-hosted runners directly on VMs does not allow us to scale it and move it from different infraestructures easily, which requires us to build our own Docker image.

Specifications

TODO

Complex Code or Requirements

TODO

Solution

Create our own Docker image with a custom entrypoint which allow us to register the workers on-the-fly and at runtime, using a specific GitHub PAT (in the meanwhile)

Otherwise we'd have to manually run this steps before raising a new runner.

Review

Reviewer Checklist

• Will the PR name make sense to users?
  • Does it need extra CHANGELOG info? (new features, breaking changes, large changes)
• Are the PR labels correct?
• Does the code do what the ticket and PR says?
  • Does it change concurrent code, unsafe code, or consensus rules?
• How do you know it works? Does it have tests?

Follow Up Work

[gustavovalverde]

Here's a sync which has over 20 hours running, with a 120 hours timeout (intermediate steps have also been removed): https://github.com/ZcashFoundation/zebra/actions/runs/5098431127/jobs/9167648586

[teor2345]

Here's a sync which has over 20 hours running, with a 120 hours timeout (intermediate steps have also been removed): ZcashFoundation/zebra/actions/runs/5098431127/jobs/9167648586

To limit Google Cloud costs, I'd suggest having a timeout that is close to the maximum time expected for the job. At the moment that's about 50-55 hours for the mainnet full sync.

[gustavovalverde]

We're no longer going to use this approach. I'll create a PR with the new one.