Fix templating fields and do_xcom_push in DatabricksSQLOperator (#27868)

When SQLExecuteQueryOperator has been introduced in #25717, it
introduced some errors in the Databricks SQL operator:

* The templated "schema" field has not been set as field in the
  operator.
* The do_xcom_push parameter was ignored

This PR fixes it by:

* storing schema as field and using it via self reference
* do_xcom_push is removed (and BaseOperator's one is used).

airflow/providers/databricks/operators/databricks_sql.py

@@ -63,7 +63,6 @@ class DatabricksSqlOperator(SQLExecuteQueryOperator):
     :param output_format: format of output data if ``output_path` is specified.
         Possible values are ``csv``, ``json``, ``jsonl``. Default is ``csv``.
     :param csv_params: parameters that will be passed to the ``csv.DictWriter`` class used to write CSV data.
-    :param do_xcom_push: If True, then the result of SQL executed will be pushed to an XCom.
     """
 
     template_fields: Sequence[str] = (
@@ -87,7 +86,6 @@ def __init__(
         http_headers: list[tuple[str, str]] | None = None,
         catalog: str | None = None,
         schema: str | None = None,
-        do_xcom_push: bool = False,
         output_path: str | None = None,
         output_format: str = "csv",
         csv_params: dict[str, Any] | None = None,
@@ -99,24 +97,28 @@ def __init__(
         self._output_path = output_path
         self._output_format = output_format
         self._csv_params = csv_params
+        self.http_path = http_path
+        self.sql_endpoint_name = sql_endpoint_name
+        self.session_configuration = session_configuration
+        self.client_parameters = {} if client_parameters is None else client_parameters
+        self.hook_params = kwargs.pop("hook_params", {})
+        self.http_headers = http_headers
+        self.catalog = catalog
+        self.schema = schema
 
-        client_parameters = {} if client_parameters is None else client_parameters
-        hook_params = kwargs.pop("hook_params", {})
-
-        self.hook_params = {
-            "http_path": http_path,
-            "session_configuration": session_configuration,
-            "sql_endpoint_name": sql_endpoint_name,
-            "http_headers": http_headers,
-            "catalog": catalog,
-            "schema": schema,
+    def get_db_hook(self) -> DatabricksSqlHook:
+        hook_params = {
+            "http_path": self.http_path,
+            "session_configuration": self.session_configuration,
+            "sql_endpoint_name": self.sql_endpoint_name,
+            "http_headers": self.http_headers,
+            "catalog": self.catalog,
+            "schema": self.schema,
             "caller": "DatabricksSqlOperator",
-            **client_parameters,
-            **hook_params,
+            **self.client_parameters,
+            **self.hook_params,
         }
-
-    def get_db_hook(self) -> DatabricksSqlHook:
-        return DatabricksSqlHook(self.databricks_conn_id, **self.hook_params)
+        return DatabricksSqlHook(self.databricks_conn_id, **hook_params)
 
     def _process_output(self, schema, results):
         if not self._output_path: