* Unpin Twisted, add a twisted-trunk tox env (without http2 for now).
* Hide the _setAcceptableProtocols import.
* Silence ScrapyClientContextFactory HTTP/1.0 warnings.
* Update ScrapyClientTLSOptions for unreleased Twisted.
* Add twisted-trunk to CI.
* Update for new changes in Twisted trunk.
* Xfail a test failing with newer Twisted.
* Test Twisted trunk with extra-deps, update the ALPN code.
* Cleanup.
* Fix typing.
* Update relevant type hints for Twisted trunk.
* Update test_no_context_sharing().
* Silence a weird mypy error.
* Update Twisted versions, unpin pyOpenSSL.
* Update a comment.
* Silence pylint.
* Make a factory fixture.
* Improve the _setAcceptableProtocols comment.
* Set OP_LEGACY_SERVER_CONNECT on new Twisted too.
* Add Twisted[http2] to extra-deps-pinned.