Fix async connection issue in BaseDatabricksHook

[Paxx2303]

Fix RuntimeError when using async operators in triggerer environment.

Problem

When DatabricksExecutionTrigger or async operators use BaseDatabricksHook in the triggerer (where an event loop is running), it causes:

RuntimeError: You cannot use AsyncToSync to run a loop in the same thread as AsyncSync

Root Cause

Async methods in BaseDatabricksHook were using the synchronous databricks_conn property which calls BaseHook.get_connection(). When called from within a running event loop, this causes the RuntimeError.

Solution

• Add aget_connection() async method wrapping BaseHook.aget_connection()
• Add a_databricks_conn async property for async connection access
• Add async helper methods: _a_get_connection_attr(), _a_endpoint_url(), _a_is_aws_federation(), _a_get_required_client_id()
• Update all async methods to use the new async connection properties
• Fix typo in proxies validation (invalid_ckeys -> invalid_keys)
• Update _a_get_aad_token() to catch aiohttp.ClientResponseError instead of requests.HTTPError

Tests

Added comprehensive async tests including:

• test_async_do_api_call_respects_schema
• test_async_do_api_call_only_existing_response_properties_are_read

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Generated-by: Claude Code (Opus 5)

[boring-cyborg]

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