Fix executor_config reference aliasing across tasks and DAGs (#72544)

[abhijeets25012-tech]

Description

Fixes #72544

_get_parent_defaults previously used copy.copy (shallow copy) when merging dag.default_args. This caused nested mutable structures, specifically executor_config, to be shared by object reference across all tasks and DAGs inheriting from those shared defaults. Consequently, runtime mutations to task.executor_config (such as setting Kubernetes pod overrides) silently modified sibling tasks and unrelated DAGs.

This PR updates _get_parent_defaults to use copy.deepcopy and explicitly deep-copies executor_config during BaseOperator initialization, ensuring strict reference isolation across task definitions.

Changes Made

• task-sdk/src/airflow/sdk/bases/operator.py:
  • Replaced copy.copy(dag.default_args) with copy.deepcopy(dag.default_args) in _get_parent_defaults.
  • Updated self.executor_config assignment in BaseOperator.__init__ to use copy.deepcopy(executor_config) to isolate both explicit and inherited configurations.

[abhijeets25012-tech]

Hi maintainers, this PR is ready for review.

Note: The failing Provider distributions tests / Compat CI jobs appear to be unrelated upstream matrix timeouts/flakes, as the changes in this PR are strictly isolated to task-sdk/src/airflow/sdk/bases/operator.py.