Urllib3-future

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- Fixed compatibility with upstream urllib3 when third party program invoke deprecated ``HTTPResponse.getheader`` or
``HTTPResponse.getheaders``. Those methods were planned to be removed in 2.1 (they still have a pending deprecation
that mention 2.1 target in the 2.3 version). As such we immediately restore the methods. (203)
- Implemented our copy of ``HTTPResponse.read1`` heavily simplified as we do already support ``HTTPResponse.read(-1)``.
Also mirrored in ``AsyncHTTPResponse.read1``.
- Automatically grab ``qh3`` for X86/i686 based processors (e.g. win32).
- Fixed the aggressive exception in our native websocket implementation when a server responded positively to an upgrade
request without the required http header. Instead of ``RuntimeError``, now raises ``ProtocolError``.

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- Fixed silencing the deprecation warning coming from python_socks about the "_socket" parameter.

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- Fixed our thread safety protection against the experimental freethreaded Python build.
As expected, the absence of GIL challenged our implementation of ``TrafficPolice`` and
took it to its knees. We reviewed the in-depht logic and improved it for maximum resilience
and performance. We backported some improvements in ``AsyncTrafficPolice`` when applicable.
- Improved error message whenever the pool capacity have been exhausted.
- Fixed background discrete watcher that never reached some connections in the pool.
- Bumped allowed upper bound for ``python-socks`` to 2.6.1 (we will have to manually increase the upper bound
each minor/patch version due to our complex integration that invoke private classes/APIs)

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- Improved our logic around caching a ssl_context in a concurrent environment.

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- Fixed error due to an internal change in python-socks 2.6
- Pinned python-socks upper bound to 2.5.3 pending further improvement into our integration.

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- Fixed an issue when trying to force load Websocket over HTTP/2 or HTTP/3.
- Ensured WebSocket via HTTP/2 with improved CI pipeline featuring haproxy as the reverse proxy.
- Fixed ``RuntimeError`` when forcing HTTP/3 by disabling both HTTP/1, and HTTP/2 and the remote is unable to negotiate HTTP/3.
This issue occurred because of our automatic downgrade procedure introduced in our 2.10.x series. The downgrade ends in panic
due to unavailable lower protocols. This only improve the UX by not downgrading and letting the original error out.
See https://github.com/jawah/niquests/issues/189 for original user report.
- Fixed negotiated extensions for WebSocket being ignored (e.g. per-deflate message).
- Backported ``HTTPResponse.shutdown()`` and nullified it. The fix they attempt to ship only concern
them, we are already safe (based on issue reproduction). See https://github.com/urllib3/urllib3/issues/2868
- Backported ``proxy_is_tunneling`` property to ``HTTPConnection`` and ``HTTPSConnection``.
See https://github.com/urllib3/urllib3/pull/3459
- Backported ``HTTPSConnection.is_verified`` to False when using a forwarding proxy.
See https://github.com/urllib3/urllib3/pull/3283
- Backported pickling support to ``NewConnectionError`` and ``NameResolutionError``.
See https://github.com/urllib3/urllib3/pull/3480