[AppGateServer] Refactor the AppGate server to use the new shannon-sdk implementation

[red-0ne]

Summary

Import and use the new shannon-sdk implementation to implement the AppGateServer.

Type of change

Select one or more:

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

Testing

Documentation changes (only if making doc changes)

• make docusaurus_start; only needed if you make doc changes

Local Testing (only if making code changes)

• Unit Tests: make go_develop_and_test
• LocalNet E2E Tests: make test_e2e
• See quickstart guide for instructions

PR Testing (only if making code changes)

• DevNet E2E Tests: Add the devnet-test-e2e label to the PR.
  • THIS IS VERY EXPENSIVE, so only do it after all the reviews are complete.
  • Optionally run make trigger_ci if you want to re-trigger tests without any code changes
  • If tests fail, try re-running failed tests only using the GitHub UI as shown here

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

[bryanchriswhite]

Preemptively approving 🔥 🚀 - only 1 question this time. 😅

[bryanchriswhite]

Why use #AllEndpoints() here instead of adding some filter function(s) - maybe #PUC?

[red-0ne]

	// AppGateServer uses the custom getRelayerUrl instead of leveraging the SDK's
	// filter to select the next endpoint to use.
	// This is because it needs to maintain the state of the last selected endpoint
	// and have a view on the original request URL to determine the next endpoint.
	// This behavior is specific to the AppGateServer and needed by clients that
	// need to instrument the endpoint selection strategy, such as the Load testing tool.

[github-actions]

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 636)
Grafana network dashboard for devnet-issue-{issue-id}