[adapters] report timestamps and history for metrics data

[abhizer]

The fix for this should be that the metrics returned the endpoint are accompanied by a timestamp such that the web console does not need to use its own clock to determine the x-value of the data points it derives throughput from.

Fixes in progressing amount of work:

• Metrics include a timestamp when they were taken
• An additional metrics endpoints like /historic-metrics that returns the last N metrics taken at a certain interval by a thread running in parallel
• An endpoint which returns any derived metrics directly by itself (e.g., throughput) rather than having the web-console calculate it

Originally posted by @snkas in https://github.com/feldera/feldera/issues/2745#issuecomment-2414487452

[blp]

This should help the UI graphs operate better in the face of pods dying and restarting.