Take screenshots with grafana image renderer

[fruch]

Monitoring stack support image renderer since scylladb/scylla-monitoring#1062
it was suggested by us in scylladb/scylla-monitoring#904

we should look into using, it would simplify, and shorten the time we need for taking screenshots at the end of the test, and in performance test where we do that multiple time during the test.

it would also can enable us capturing of specific panels, for use case it's more relevant

Ref: scylladb/scylla-monitoring#1062
Ref: scylladb/scylla-monitoring#904

• build a POC
• remove the current selenium based code (drop raindrop snapshots on the way ? not really used those days, cause collecting of the monitoring stack works good enough for us)

[fruch]

a POC of how it should work:

• feature(monitoring): take screenshots with grafana image renderer #7503

[fruch]

completed in #7503