Add configuration support for aiohttp.ClientSession kwargs (e.g. trust_env) in deferrable operators / triggerer

### Description Airflow should provide a global supported config mechanism to pass additional kwargs to aiohttp.ClientSession at construction time. For example, an Airflow config key — e.g. `[aiohttp] trust_env = True` in airflow.cfg, read by a shared session factory used across all providers. ### Use case/motivation ## Problem Deferrable operators that use `aiohttp` internally (e.g. `SnowflakeSqlApiOperator`, and others backed by async HTTP clients) create `aiohttp.ClientSession` instances without passing `trust_env=True`. This means they silently ignore proxy-related environment variables (`HTTPS_PROXY`, `HTTP_PROXY`, `NO_PROXY`) set in the execution environment. In managed environments like AWS MWAA — where corporate proxy settings are injected via a startup script into environment variables — this causes triggers to bypass the proxy entirely and time out, while synchronous operators using requests or urllib work correctly. ## Current workaround You can set `trust_env` globally via a Monkey-patch of `aiohttp.ClientSession.__init__` in `airflow_local_settings.py`: ```python import aiohttp from typing import Any _original_init = aiohttp.ClientSession.__init__ def _trust_env_init(self: aiohttp.ClientSession, *args: Any, **kwargs: Any) -> None: kwargs.setdefault("trust_env", True) _original_init(self, *args, **kwargs) aiohttp.ClientSession.__init__ = _trust_env_init ``` This is fragile, not discoverable, and should not be necessary for what is effectively a standard proxy configuration requirement. ## Environment Version: Apache Airflow 3.x (probably also affects 2.x) Provider: apache-airflow-providers-snowflake (and any other provider using aiohttp in triggers) Deployment: AWS MWAA (corporate proxy injected via startup script env vars) ## Impact Any organisation running Airflow behind a corporate proxy will hit this silently — deferrable operators time out with no clear indication that proxy settings are being ignored. ### Related issues _No response_ ### Ar…