Play Framework

chore(utils): delete ExecutorFacade

Step 3/5 toward VT-only. With VT execution unconditional, the dual-mode
dispatch facade has nothing to dispatch between. Invoker.scheduler and
JobsPlugin.scheduler change type from ExecutorFacade to
VirtualThreadScheduledExecutor (volatile field, assigned by init/start,
nulled by stop) and callers invoke its methods directly.

API changes:
- Invoker.scheduler / JobsPlugin.scheduler: ExecutorFacade -> VTScheduledExecutor
- VTScheduledExecutor gains shutdownGracefully(long timeoutMs) — ported
  from the deleted ExecutorFacade so JobsPlugin.onApplicationStop keeps
  the same drain semantics.
- Job.executor identity comparison: was scheduler.platformExecutor() /
  virtualExecutor(); now scheduler directly.

Removed:
- framework/src/play/utils/ExecutorFacade.java
- framework/test-src/play/utils/ExecutorFacadeTest.java
- The if-isUsingVirtualThreads / platformExecutor() branches in
  Invoker.invoke / Invoker.invoke(millis) / Invoker.resetClassloaders
  (resetClassloaders becomes a no-op under VT-only — VTs aren't
  enumerable and each one sets its CL freshly per task).
- WaitForTasksCompletion's polling thread + Map<Future, Invocation> queue
  (the legacy 50ms-scan loop). The VT-block-and-resume path is the only
  path now; no instance, no run() method, no queue field. The class
  retains the static waitFor() entry point as a logical grouping.
- Unused imports: PThreadFactory and the now-orphan java.util.concurrent
  classes from Invoker.

Test fixups:
- InvokerVirtualThreadTest, VirtualThreadIntegrationTest,
  JobsPluginVirtualThreadTest: facade-API assertions
  (isUsingVirtualThreads, platformExecutor, virtualExecutor) replaced
  with `scheduler != null`.

ant test passes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>