refactor: replace scheduler factory functions with mixin pattern

Replace _create_pooling_scheduler() and _create_chunked_prefill_scheduler()
factory functions with PoolingSpyreMixin and ChunkedPrefillSpyreMixin classes.

Each mixin uses _is_async_scheduler() (isinstance check) to detect the concrete
base class at runtime and adjust behaviour accordingly, instead of capturing
is_async via a closure variable.

Concrete classes use simple multiple inheritance:

  class PoolingSpyreScheduler(PoolingSpyreMixin, Scheduler): pass
  class AsyncPoolingSpyreScheduler(PoolingSpyreMixin, AsyncScheduler): pass
  class ChunkedPrefillSpyreScheduler(ChunkedPrefillSpyreMixin, Scheduler): pass
  class AsyncChunkedPrefillSpyreScheduler(ChunkedPrefillSpyreMixin, AsyncScheduler): pass

Side effects:
- __module__/__name__/__qualname__ fixup blocks removed (no longer needed)
- _async_warning_logged flag removed (debug log emitted each call is fine)
- TYPE_CHECKING import removed (unused after refactor)

Signed-off-by: Avishek Goswami <[email protected]>

Author: Avishek Goswami

tests/utils/test_platform_validation.py

@@ -250,6 +250,8 @@ def test_flex_device_set_for_sendnn_compile_only(self, monkeypatch):
         mock_vllm_config.scheduler_config.max_num_batched_tokens = 64
         mock_vllm_config.model_config.max_model_len = 128
         mock_vllm_config.scheduler_config.max_num_seqs = 2
+        mock_vllm_config.scheduler_config.scheduler_cls = None
+        mock_vllm_config.scheduler_config.async_scheduling = False
 
         # Call check_and_update_config which should set FLEX_DEVICE
         SpyrePlatform.check_and_update_config(