Migrate to a new method for running the Secretless health check

[izgeri]

Description

At current Secretless relies on github.com/heptiolabs/healthcheck in its util pkg, but the project was last updated 3 years ago and isn't all that complex. We should either implement a simple version of the needed functionality in our own project or look for a better maintained / modern library.

AC:

• Replace the heptiolabs/healthcheck project with something else that will be maintained

[sgnn7]

I'm a bit iffy on this - lack of updates doesn't mean to me that it lacks the features we need I suppose. Better healthcheck would be welcome though where it would show the status and listing of all the connectors.