zero/healthchecks: add checks for ability to save bootstrap parameter and bundle status reporting

[wasaga]

Summary

Adds some more Zero health checks:

• resource bundle status
• bootstrap file persistence

Related issues

Fixes:

• https://github.com/pomerium/pomerium-zero/issues/2111
• https://github.com/pomerium/pomerium-zero/issues/2108

User Explanation

Checklist

• reference any related issues
• updated docs
• updated unit tests
• updated UPGRADING.md
• add appropriate tag (improvement / bug / etc)
• ready for review

[coveralls]

coverage: 56.863% (+0.04%) from 56.822%
when pulling 20c229b on wasaga/hc-zero-bootstrap-and-resource-bundle
into 25aceea on main.