ci: consolidate conformance and build jobs

[2color]

What this PR does

Consolidates the Gateway conformance test workflow with the test and release

Why

• To avoid having weird cross workflow dependencies.
• Initially this was done to avoid race conditions between the two workflows that were both running on main concurrently and attempting to commit to the repo (report.json and the release commit) and one of the commits would fail.

• 533 solves the problem of making the frontend dependent on the conformance tests results (which weren't being used anyways). So maybe this PR is not needed and we can keep the two separated?

Open questions

• What's the point of having the conformance tests here? The results in the report seem to be wrong, and we are not displaying the results anyways.
• Even if we run the conformance tests, why do we need to commit the results to this repo?

Related to #530

[2color]

Closing this since the conformance tests as this is no longer relevant.

The conformance test results have many failures that are not presented in any meaningful way.

I don't think it makes sense anymore to consolidate the two workflows.