Migrate to new prometheus client

[kziel1]

Last update of prometheus simpleclient was at 2022. The old dependency stack hinders updates in the company I work for. It would be a big value for me to know if prometheus client update is planned or respective PR would be integrated (beware: breaking changes, like different Collector implementation, MetricFamily, etc.).

https://prometheus.github.io/client_java/migration/simpleclient/

[kziel1]

An attempt of Proof of Concept for Migration to the new prometheus client:
#2223
Generating a sample value hasn't been translated, hence tests not compiling.

[IRus]

Do you think it's possible to keep integration with both versions of Prometheus, so users can decide which one to use for a few years while transition happens?

[kziel1]

Even if theoretically one would get both to run at the same time (since it's a new package, not a version update, so there would be no fun needed with shading etc.), you would still be getting some the deprecation warnings and artifacts convergence errors (depending how your pipeline is configured) if not now, then shortly in the future. And I don't guarantee that gathering twice as much of counters and buckets (because of the new model) won't affect performance.

[kziel1]

Some other option would be to run a parallel release pipeline of HikariCP with the new prometheus implementation

[kziel1]

Adjusted most of the tests. Since breaking changes were introduced via simpleclient->prometheus->micrometer, there are some changes that may need to be revised (like quantiles assertions that changed behaviour). Registry tests mostly passed, apart from deregistering/closing of trackers.
#2223