asgi: get valid/invalid http tests to pass

[pajod]

There are 101 perfectly fine HTTP test cases in tests/requests/**.http many of which of no use for testing the ASGI workers right now. Let's fix that.

• change asgi HTTP error exceptions to match base sync worker
  • did not look intentional, link to diff in PR here: Add native ASGI worker and uWSGI binary protocol support #3444 (comment)
• use StopAsyncIteration in async def
  • my reasoning here is that sticking with this signalling is exclusively practical when the exception can bubble in async iterator
• override config in cases tests/test_asgi.py::MockConfig has non-default
  • those test cases actually care about the configs set there, and though this could equally be fixed by switching the test to use the default settings instead, explicit is better than implicit

(updated tests/treq.py and new tests/test_nginx.py intentionally omitted here, they match most of my parallel PRs)

[pajod]

Not resolved here (because invalid requests were never checked as thoroughly as valid ones - so its not strictly needed for those tests), but a good candidate after some refactoring: dumping a traceback inplace of logging the warning and responding

gunicorn.http.errors.InvalidRequestLine: Invalid HTTP request line: ''

[benoitc]

i suggest to wait for the deduplication refactoring . Coming week I will release the 25.0?0 with current state. Then what about making it for 25.1 ?