Play Framework

chore(utils): delete VirtualThreadConfig + deprecated executor mirrors

Step 4/5 toward VT-only. Removes:
- framework/src/play/utils/VirtualThreadConfig.java
- framework/test-src/play/utils/VirtualThreadConfigTest.java
- Invoker.executor (was deprecated mirror of platform pool)
- Invoker.virtualExecutor (was deprecated mirror of scheduler)
- Invoker.usingVirtualThreads (was deprecated mirror)
- JobsPlugin.executor / virtualExecutor / usingVirtualThreads (same)
- Now-unused imports: VirtualThreadConfig from Invoker / Mail,
  ScheduledThreadPoolExecutor from Invoker.

Behavioral additions:
- Play.java emits a WARN at boot for every play.threads.virtual* property
  remaining in application.conf, telling the operator the key is no longer
  honored. One-shot per boot; doesn't block startup.

Other-module fix:
- modules/console InfoConsole was reading JobsPlugin.executor; updated to
  read JobsPlugin.scheduler (the field that replaced it).

ant test passes.

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