Restructure tests to be chainable and cover more cases

[clux]

• refactored test handlers to be invoked via a Scenario enum in fixtures
• ApiServerVerifier::run(scenario) only pub entry point to be run once per test
• each scenario can invoke invidual handlers more than once

Handles a lot more error cases:

• expects reconcile output directly (with note about Closed error)
• awaits the mocksrv's JoinHandle (ensuring everything happens)
• with timeout to give good output when expecting too much

also test better now:

• deletion covered
• event publishing checked for expected reason