Rubify health check script

[LesnyRumcajs]

Issue summary

Currently, the health check script is written in bash. For readability and extendability and having a uniform technology in the sync check, it would be great to rewrite it in Ruby. The current script doesn't do any magic, just grabs the metrics and compares a few values there, so it should be straightforward to implement.

It might be an excellent entry task to get exposed to Ruby.

Task summary

• [ ] rewrite health check script in Ruby
• [ ] verify that it works the same way as the former bash script (perhaps some basic unit tests?)
• [ ] use it in sync check CI

Acceptance Criteria

• [ ] bash script is no longer used in sync check
• [ ] new version has at least the same functionality as the former one

Other information and links

https://github.com/ChainSafe/forest/pull/1867