Run Operator tests with the latest Manager before release

[mikliapko]

Operator test suite - https://github.com/scylladb/scylla-operator/tree/master/test/e2e/set

The suite can be run with a different manager version by sending a dummy PR updating the manager and manager agent image tags (like here scylladb/scylla-operator#2089 or here scylladb/scylla-operator#2105).

Also, we need to investigate whether available Operator SCT tests are able to discovery recently found Manager regression issues: #4028 and #3989

[karol-kokoszka]

The regression with Scylla Manager that was found by Operator tests came from Operator repo tests, not from SCT.
The best would be to have possibility of integrating with what they have in their repo.

cc: @zimnx @tnozicka

[tnozicka]

I am planing to setup "latest" integration jobs between the projects (now that we have the unified config).

[tnozicka]

scylladb/scylla-operator#1611
(there can be other variants when its configurable with the first job)