ci: add curl-for-win builds: Linux MUSL, macOS, Windows

[vszakats]

Linux MUSL (llvm/clang), macOS Apple clang, Windows (llvm/clang).

Configured with HTTP/2 and HTTP/3 and other dependencies (the default
curl-for-win) for a comprehensive build test.

curl 8.8.0-DEV (x86_64-unknown-linux-musl) libcurl/8.8.0-DEV LibreSSL/3.9.1 zlib/1.3.1 brotli/1.1.0 zstd/1.5.6 libpsl/0.21.5 libssh2/1.11.0 nghttp2/1.61.0 ngtcp2/1.4.0 nghttp3/1.2.0
Protocols: dict file ftp ftps gopher gophers http https imap imaps ipfs ipns mqtt pop3 pop3s rtsp scp sftp smb smbs smtp smtps telnet tftp ws wss
Features: alt-svc AsynchDNS brotli HSTS HTTP2 HTTP3 HTTPS-proxy IPv6 Largefile libz NTLM PSL SSL threadsafe UnixSockets zstd

curl 8.8.0-DEV (x86_64-apple-darwin) libcurl/8.8.0-DEV LibreSSL/3.9.1 zlib/1.3.1 brotli/1.1.0 zstd/1.5.6 libpsl/0.21.5 libssh2/1.11.0 nghttp2/1.61.0 ngtcp2/1.4.0 nghttp3/1.2.0
Protocols: dict file ftp ftps gopher gophers http https imap imaps ipfs ipns ldap ldaps mqtt pop3 pop3s rtsp scp sftp smb smbs smtp smtps telnet tftp ws wss
Features: alt-svc AsynchDNS brotli HSTS HTTP2 HTTP3 HTTPS-proxy IPv6 Largefile libz NTLM PSL SSL threadsafe UnixSockets zstd

curl 8.8.0-DEV (x86_64-w64-mingw32) libcurl/8.8.0-DEV LibreSSL/3.9.1 zlib/1.3.1 brotli/1.1.0 zstd/1.5.6 WinIDN libpsl/0.21.5 libssh2/1.11.0 nghttp2/1.61.0 ngtcp2/1.4.0 nghttp3/1.2.0
Protocols: dict file ftp ftps gopher gophers http https imap imaps ipfs ipns ldap ldaps mqtt pop3 pop3s rtsp scp sftp smb smbs smtp smtps telnet tftp ws wss
Features: alt-svc AsynchDNS brotli HSTS HTTP2 HTTP3 HTTPS-proxy IDN IPv6 Kerberos Largefile libz NTLM PSL SPNEGO SSL SSPI threadsafe UnixSockets zstd

Limited to x64, because for build testing the additional CPUs don't add
much value compared to the extra build time. They can be enabled easily
if deemed useful.

To the extent of curl-for-win configuration options, it's trivial to add
further build combinations.

Closes #13335

[vszakats]

To the extent of curl-for-win build options, it's trivial to add further build combinations.

E.g. for gcc, with debug, with GLIBC, SecureChannel or Schannel, without H3, without H2,
without zlib, zstd, brotli, IDN, SSH, or with libssh instead of libssh2. quictls, OpenSSL 3 + QUIC.
It's also possible to do non-TLS builds, or minimal builds with almost no options. Alpine
images are also supported. In theory also MSYS2, but I haven't tried those for a long time.
MultiSSL is also supported.

Supported CPUs: arm64 (Linux, macOS, Windows), riscv64 (Linux) and x86 (Windows).

Complete list of options:
https://github.com/curl/curl-for-win/blob/80bd09bcdcff618babe9befd930e1016eca6367e/_build.sh#L34-L78

All builds use CMake, they are all out-of-tree and does cross-build when necessary.