[Relay Mining] Emit events and refactor test helpers

[Olshansk]

Summary

• Event - Emitting an event when the relay mining difficulty is updated
• Flaky - Added some flaky comments/pointers in different places
• Refactor - the event filtering function into a shared location
• Utils - Updated testing to support a signed mined relay

Issue

• 542

Type of change

Select one or more:

• [x] New feature, functionality or library
• [ ] Bug fix
• [x] Code health or cleanup
• [ ] Documentation
• [ ] Other (specify)

Testing

• [ ] Unit Tests: make go_develop_and_test
• [ ] LocalNet E2E Tests: make test_e2e
• [ ] DevNet E2E Tests: Add the devnet-test-e2e label to the PR.

Sanity Checklist

• [ ] I have tested my changes using the available tooling
• [ ] I have commented my code
• [ ] I have performed a self-review of my own code; both comments & source code
• [ ] I create and reference any new tickets, if applicable
• [ ] I have left TODOs throughout the codebase, if applicable

[Olshansk]

@bryanchriswhite @red-0ne Few things to note in this PR:

1. The actual business logic was short & simple
2. A lot of work went into making the integration test work
3. A lot of improvements were made to the utilities in a way that existing ones were reused & refactored
4. @bryanchriswhite Special request - please make a mental note of all the TODOs in case you come up with better ideas in the future
5. @red-0ne Special request - see the TODOs in the code related to the telemetry. I will ask you to implement it on my behalf due to time limitations & because I'd like to present it at EthCC

[Olshansk]

@bryanchriswhite @red-0ne LOVE the comments on this! Ready for another review but also beginning to look much better after all your suggestions 🚀

[github-actions[bot]]

The CI will now also run the e2e tests on devnet, which increases the time it takes to complete all CI checks.

You may need to run make trigger_ci to submit an empty commit that'll trigger the tests.

GCP workloads (requires changing the namespace to 610)) Grafana network dashboard for devnet-issue-{issue-id}