add default http health check

[hassenius]

What this PR does / why we need it:

This is an initial draft to get feedback from maintainers.

Current health checks do not fail if nginx stop responding on default http port (meaning it is not healthy from an end-users perspective).

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• CVE Report (Scanner found CVE and adding report)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation only

Which issue/s this PR fixes

fixes #9067

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Checklist:

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[hassenius]

@rikatz @ElvinEfendi before I put more effort into this, would like to get feedback if you feel this is a suitable approach to addressing cases where nginx has issues responding to user traffic (i.e. port 80), but still responds to the healthcheck port.

There are demonstratable cases where this occurs, and the current health check implementation does not pick that up.

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[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: hassenius
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[botchk]

Trying to push this improvement suggestion a bit. We had a situation where nginx configuration reload resulted in an invalid configuration due to a load_module not being able to find a particular library. Nginx was not able to handle requests but due to the liveness probe being healthy, it still got forwarded traffic by the service.

Extending the health check like that should also mitigated issues like that!

[rikatz]

/ok-to-test

Please rebase over main and ping me on Slack to further review.