Description of problem: Implement Prometheus on RHOSP using Agent mode (TSDB disabled; ephemeral scrape-and-push model that doesn't require external or persistent storage). 

Scrape collectd via write_prometheus. Scrape ceilometer via pushgateway (to be determined if ceilometer connects to a remote pushgateway hosted off-cluster or a local pushgateway implementation is provided).

Needs to implement the following:

- leverage Prometheus v2.32.0 or later which implements Agent feature (ose-prometheus?)
- add ansible logic to control deployment of Prometheus in agent mode, configured with appropriate flags and ServiceMonitor configuration to scrape the various endpoints
- implement a strategy to distribute certificates so that connections can be secured to the remote-write receiver