refactor: cleanup CI inconsistencies

[kb-newrelic]

Summary

• Fast-follow cleanup for things I noticed during review of test: add nightly fips goreleaser and workflow #397 and related fips PRs that weren't necessary part of that PR:

Tests

• Remove unused values from nr_backend char
• Changed terminology of deploy_id to test_key as that is the context the value is used in now.
• Cleaned up some method naming that was still tied to us using the hostname (instead of the testKey) as identifier for telemetry

CI / Makefiles

• Avoid unnecessary source generation in licenses-check by checking for existence of _build. Solving this with target dependencies would've required to make generate-sources aware of all its dependencies. While that's possible, it's also a big risk for this to get outdated over time, potentially leading to unintentionally skipping source generation, so I decided to keep it a phony target for now.
• Restructure Makefile as we've shifted the compilation completely to goreleaser.
  • distro-specific targets contain the distro in the target name to distinguish them from general targets. Some general targets are just delegations to distro-specific targets
  • remove build targets, only generate-sources-... remain
  • add pre/post-sourcegen-targets to make that distinction in checks clear
  • mark phony targets as actual phony
  • remove unused generate target
  • add clean targets
• Fix ensure-goreleaser-up-to-date as it wasn't checking for all goreleaser files (nightly fips was actually outdated)

[kb-newrelic]

With east coast team members, we want this running a bit earlier.
Should also move the nightly fips workflow up once merged.