OSO: pull data from OSO prometheus server

[fche]

There are indications that some of our target OSO clusters may expose a usable prometheus-server federation-type webapi, via which we might be able to pull in a least basic container-level system data. We need information & testing to see this work (@kbsingh), and then some pcp work in order to exploit it.

performancecopilot/pcp#444

[fche]

performancecopilot/pcp#434 becoming important

[goodwinos]

@fche, is this blocked on PCP due to performancecopilot/pcp#444 (which is resolved now that we can specify http get headers in pmdapromethes URL configs), or some other issue?

[fche]

Good point, at this point we're more blocked by trying to find a configuration of pmdaprometheus instance(s) that can support the load, after the draft patches we now have for performancecopilot/pcp#434 .

[fche]

change of plans moot this task