php#64: Refactor deadlock detection to use structured exceptions instead of warnings

          - Add new Async\DeadlockError exception class extending Error
          - Replace multiple async_warning() calls with single structured exception
          - Implement proper exit_exception handling for inter-coroutine safety
          - Update resolve_deadlocks() to set ZEND_ASYNC_EXIT_EXCEPTION correctly
          - Add ZEND_ASYNC_EXCEPTION_DEADLOCK to async class enum (ID: 36)
          - Extend async_get_class_ce() to support new exception type
          - Update all deadlock tests to expect exception instead of warnings
          - Fix memory leak by removing unnecessary GC_ADDREF calls

          This change improves error handling by providing a single, catchable
          DeadlockError exception instead of multiple warnings, while maintaining
          proper coroutine cancellation behavior through exit_exception mechanism.

          Tests updated:
          - 001-deadlock-basic-test.phpt
          - 002-deadlock-with-catch.phpt
          - 003-deadlock-with-zombie.phpt
          - 010-deadlock-after-cancel-with-zombie.phpt

Author: EdmondDantes

Zend/zend_async_API.h

@@ -132,6 +132,7 @@ typedef enum {
 	ZEND_ASYNC_EXCEPTION_INPUT_OUTPUT = 33,
 	ZEND_ASYNC_EXCEPTION_POLL = 34,
 	ZEND_ASYNC_EXCEPTION_DNS = 35,
+	ZEND_ASYNC_EXCEPTION_DEADLOCK = 36,
 } zend_async_class;
 
 /**