Speed up integration tests (#732)

Speed up the integration tests by caching the dag bag result.

Previously, for each parametrized dag run test, it would reparse all of
the dags, which takes a non-trivial amount of time to parse all of the
cosmos example dags.

On my local machine, the total time went from 1616s to 540s, which will
save a good amount of GH minutes 😃.

tests/test_example_dags.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from pathlib import Path
+from functools import cache
 
 import airflow
 import pytest
@@ -37,6 +38,7 @@ def session():
     return get_session()
 
 
+@cache
 def get_dag_bag() -> DagBag:
     """Create a DagBag by adding the files that are not supported to .airflowignore"""
     with open(AIRFLOW_IGNORE_FILE, "w+") as file:

tests/test_example_dags_no_connections.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from pathlib import Path
+from functools import cache
 
 import airflow
 import pytest
@@ -23,6 +24,7 @@
 }
 
 
+@cache
 def get_dag_bag() -> DagBag:
     """Create a DagBag by adding the files that are not supported to .airflowignore"""
     with open(AIRFLOW_IGNORE_FILE, "w+") as file: