fix(python): settle cancelled tasks awaited by async workflows

[dbrattli]

Python Async.AwaitTask lets asyncio.CancelledError escape its completion callback because that exception derives from BaseException. A cancelled task can therefore leave its waiting workflow unsettled. The existing cancellation test returned through Async.StartImmediate before its assertion ran, closing its event loop before a background cancellation timer fired and producing a thread warning during a later test.

Compile Async.AwaitTask to a new await_task_with_cancellation entry point that reports native task cancellation as TaskCanceledException through the error continuation, matching .NET. Add the Python exception type and compiler mapping, including message and inner-exception support. Preserve the legacy await_task entry point for existing Python consumers; newly generated code requires the runtime containing the new entry point.

Replace the cancellation test with an awaited test that uses a child-entry handshake and checks the error outcome on both .NET and Python. Add native coverage for tasks cancelled before and during the wait, plus an F# regression for the exception type and payload.

[github-actions]

Python Type Checking Results (Pyright)

Metric	Value
Total errors	34
Files with errors	4
Excluded files	4
New errors	✅ No

Excluded files with errors (4 files)

These files have known type errors and are excluded from CI. Remove from pyrightconfig.ci.json as errors are fixed.

File	Errors	Status
temp/tests/Python/test_hash_set.py	18	Excluded
temp/tests/Python/test_applicative.py	12	Excluded
temp/tests/Python/test_nested_and_recursive_pattern.py	2	Excluded
temp/tests/Python/fable_modules/thoth_json_python/encode.py	2	Excluded