Wait for dependent lifecycle shutdown callbacks - #37340

Closes gh-28277.

DefaultLifecycleProcessor sizes each shutdown latch from the beans in one phase, but dependent beans in other phases decrement the same latch. A fast dependent can therefore let close() return while another shutdown callback is still pending.

Register shutdown participants with a Phaser as beans are stopped, including their dependents. Keep one coordinator registered until all stop calls have been issued so synchronous callbacks cannot end the wait early. Phase timeouts and interruption handling are preserved.

Regression tests defer either the higher-phase or the dependent bean's callback and verify that shutdown waits. Another test verifies that a dependent bean cannot prevent shutdown after the configured timeout.

Validation: :spring-context:check passes. All 27 DefaultLifecycleProcessorTests pass with -PtestGroups=LONG_RUNNING. Enabling that group for the whole module exposes two failures in BackgroundBootstrapTests.bootstrapWithCustomExecutorAndLazyConfig and EnableSchedulingTests.withExplicitScheduler; both reproduce on unmodified main at 93ff61fb1f.