Avoid FluxReplay buffer retaining/leaking with tiny TTL

[simonbasle]

• WIP Sinks.many().replay().limit(Duration.ZERO) leaks memory #2994 FluxReplay Duration.ZERO leak
• Avoid FluxReplay retaining by progressively applying removals

[simonbasle]

note: in the test class, on top of the additional 4 tests, a few polishing changes have been made:

• moved the abstract test configuration up at the top again so that "this is the beginning of tests" comment makes sense
• turned info-level logging into debug level logging to avoid logging spam
• avoid setting up the VirtualTimeScheduler if no time manipulation is done in the test (via @Tag annotation and TestInfo checking)

[reactorbot]

@simonbasle this PR seems to have been merged on a maintenance branch, please ensure the change is merge-forwarded to intermediate maintenance branches and up to main 🙇