Feature Request: Make monitoring configurable through API

### Checklist

- [x] I did not find a related open enhancement request.
- [x] I understand that enhancement requests filed in the GitHub repository are by default low priority.
- [x] If this request is time-sensitive, I have submitted a corresponding issue with [GCP support](https://cloud.google.com/support-hub).

### Describe the feature

Config Sync currently sends a list of metrics to GCM (Google Cloud Monitoring) if GKE default credential is detected, the pipeline is enabled by default and is tedious to turn off, see https://github.com/GoogleContainerTools/config-sync/blob/main/docs/custom-metric-filter.md.

We suggest the metrics pipeline to be configurable through Rsync API.

### Importance

_No response_