This patch simplifies the worker lifecycle and focuses on using interruption
instead of various flags to manage cancellation. This should enable workers to
cancel themselves more quickly, and is particularly important when they may
be waiting for a resource to become available (such as merge buffers as in apache#18075).

Changes:

1) Introduce WorkerRunRef to manage worker execution and cancellation. This class
   encapsulates the logic for running a worker in an executor and canceling it
   via thread interruption.

2) Move periodic controller status checking out of IndexerWorkerContext and into
   a dedicated PeriodicControllerChecker class.

3) Remove stop(), awaitStop(), and controllerFailed() from the Worker interface.
   Workers are now canceled via interruption only.

4) Remove controllerAlive tracking from WorkerImpl. It should no longer be necessary
   now that workers are interrupted on controller failure.

* Dart: Wait for a merge buffer if none is available.

For Dart-only workloads, it is not possible for merge buffers to be
exhausted, because the number of concurrent queries is capped at the
number of merge buffers by DartWorkerMemoryManagementModule. However,
When native and Dart queries are run on the same Historical, it is
possible for buffers to be held by native queries. In this case, Dart
workers must wait for buffers to become available.

This waiting now happens in the worker runner thread, and lasts for the
configured query timeout. At this time, the waiting is not interrupted
when a cancellation request arrives from the controller. This should be
addressed in another patch.

* Add test coverage for DartProcessingBuffersProvider.

* Changes from review.

* Add tests.

* More tests.

* MSQ: Use interrupts for worker cancellation.

This patch simplifies the worker lifecycle and focuses on using interruption
instead of various flags to manage cancellation. This should enable workers to
cancel themselves more quickly, and is particularly important when they may
be waiting for a resource to become available (such as merge buffers as in #18075).

Changes:

1) Introduce WorkerRunRef to manage worker execution and cancellation. This class
   encapsulates the logic for running a worker in an executor and canceling it
   via thread interruption.

2) Move periodic controller status checking out of IndexerWorkerContext and into
   a dedicated PeriodicControllerChecker class.

3) Remove stop(), awaitStop(), and controllerFailed() from the Worker interface.
   Workers are now canceled via interruption only.

4) Remove controllerAlive tracking from WorkerImpl. It should no longer be necessary
   now that workers are interrupted on controller failure.

* Style fixes.

* Dart: Wait for a merge buffer if none is available.

For Dart-only workloads, it is not possible for merge buffers to be
exhausted, because the number of concurrent queries is capped at the
number of merge buffers by DartWorkerMemoryManagementModule. However,
When native and Dart queries are run on the same Historical, it is
possible for buffers to be held by native queries. In this case, Dart
workers must wait for buffers to become available.

This waiting now happens in the worker runner thread, and lasts for the
configured query timeout. At this time, the waiting is not interrupted
when a cancellation request arrives from the controller. This should be
addressed in another patch.

* Add test coverage for DartProcessingBuffersProvider.

* Changes from review.

* Add tests.

* More tests.

* MSQ: Use interrupts for worker cancellation.

This patch simplifies the worker lifecycle and focuses on using interruption
instead of various flags to manage cancellation. This should enable workers to
cancel themselves more quickly, and is particularly important when they may
be waiting for a resource to become available (such as merge buffers as in apache#18075).

Changes:

1) Introduce WorkerRunRef to manage worker execution and cancellation. This class
   encapsulates the logic for running a worker in an executor and canceling it
   via thread interruption.

2) Move periodic controller status checking out of IndexerWorkerContext and into
   a dedicated PeriodicControllerChecker class.

3) Remove stop(), awaitStop(), and controllerFailed() from the Worker interface.
   Workers are now canceled via interruption only.

4) Remove controllerAlive tracking from WorkerImpl. It should no longer be necessary
   now that workers are interrupted on controller failure.

* Style fixes.