refactor: move healthcheck middleware early in the pipeline

What does this MR do?

Abstract out an healthcheck middleware and move it early in the pipeline.
Add Cache: no-store when returning healthcheck responses and don't add custom headers to it.

TestHealthCheckMiddleware has also been expanded to cover more cases.

TODO

• I added the Changelog trailer (e.g. Changelog: feature) to the commits that need to be included in the changelog
• I added unit tests or they are not required
• I added acceptance tests or they are not required
• I added documentation (or it's not required)
• I followed code review guidelines
• I followed Go Style guidelines