Custom Prefix for Prometheus Process Metrics

[karlem]

Users have requested enabling Prometheus process metrics (see #1180), but unfortunately, these metrics are registered with the default registry, which prevents control over the prefix (also requested by users in #1172). While we can enable process metrics for now, addressing the prefix issue is essential moving forward.

Possible Solutions:
Wait for or implement a solution in the Prometheus library (see rust-prometheus issue #518).
Use an alternative implementation of metrics, such as metrics-process.