* Upgrade baseline curl to 8.1.1
New curl version includes bugfixes, new options but mainly websocket
support which was long requested in curl impersonate. Upstream curl
reworked a lot of their http2 code which necessitated a lot of changes
on our side as well.
* Fix build on mac due to bad header priorities
On macos, clang gives priority to /usr/local/include
over locations specified with -isystem for some unknown reason. In turn
this causes clang to use the system's openssl, which conflicts with
curl-impersonate's boringssl headers.
To prevent that, disable curl's automatic conversion of -I flags to
-isystem.
* Upgrade zlib version
* Upgrade GitHub Mac runner to macos-12
* Upgrade nghttp2 version to 1.56.0
curl-8.1.1 uses an nghttp2 function that only exists in newer versions
of nghttp2.
