Fix Azure Batch Hook instantation (#33731)

The Hook instantiation for Azure Batch has been done in the
constructor, which is wrong. This has been detected when #33716 added
example dag and it started to fail provider imports as connection
has beeen missing to instantiate it.

The hook instantiation is now moved to cached property.

airflow/providers/microsoft/azure/operators/batch.py

@@ -17,6 +17,7 @@
 # under the License.
 from __future__ import annotations
 
+from functools import cached_property
 from typing import TYPE_CHECKING, Any, Sequence
 
 from azure.batch import models as batch_models
@@ -176,7 +177,10 @@ def __init__(
         self.timeout = timeout
         self.should_delete_job = should_delete_job
         self.should_delete_pool = should_delete_pool
-        self.hook = self.get_hook()
+
+    @cached_property
+    def hook(self):
+        return self.get_hook()
 
     def _check_inputs(self) -> Any:
         if not self.os_family and not self.vm_publisher:

tests/providers/microsoft/azure/operators/test_azure_batch.py

@@ -162,6 +162,7 @@ def setup_method(self, method, mock_batch, mock_hook):
         self.batch_client = mock_batch.return_value
         self.mock_instance = mock_hook.return_value
         assert self.batch_client == self.operator.hook.connection
+        assert self.batch_client == self.operator2_pass.hook.connection
 
     @mock.patch.object(AzureBatchHook, "wait_for_all_node_state")
     def test_execute_without_failures(self, wait_mock):