Support for asserting timers in testkit

[johanandren]

Yeah, timers will be easy to do in the testkit as well, as they can just be a stored list of scheduled timers to assert happened or not after a call. I don't think that should be held up by missing support for async.exec-calls, which are quite different, not having a solution.

That would mean a dummy timer service impl in the testkit action runner with access through the ActionTestKit

Originally posted by @johanandren in https://github.com/lightbend/kalix-jvm-sdk/pull/921#discussion_r862665266