Refactor http.py with explicit arguments

[HundredVisionsGuy]

Created new sansio/http module. The current top-level http module will invoke sansio/http with explicit argument

• fixes refactor WSGI assumptions out of http.py and wsgi.py functions #2408

Checklist:

• Add tests that demonstrate the correct behavior of the change. Tests should fail without the change.
• Add or update relevant docs, in the docs folder and in code.
• Add an entry in CHANGES.rst summarizing the change and linking to the issue.
• Add .. versionchanged:: entries in any relevant code docs.
• Run pre-commit hooks and fix any issues.
• Run pytest and tox, no tests failed.

[pgjones]

I think we should squash the commits into one.

[rrahkola]

We squashed the commits as requested, but the check for "Tests/3.11-dev" failed three tests. Looking at the test result, we don't understand how our code would cause these failures. Maybe these failures are related to #2421 ?

Could you please advise?