Similarly to the QUIC API originated in BoringSSL, this API allows
to register custom TLS callbacks for an external QUIC implementation.
See the SSL_set_quic_tls_cbs manual page for details.

Due to a different approach used in OpenSSL 3.5, handling of CRYPTO
frames was streamlined to always write an incoming CRYPTO buffer to
the crypto context.  Using SSL_provide_quic_data(), this results in
transient allocation of chain links and buffers for CRYPTO frames
received in order.  Testing didn't reveal performance degradation of
QUIC handshakes, https://github.com/nginx/nginx/pull/646 provides
specific results.

All definitions now set in ngx_event_quic.h, this includes moving
NGX_QUIC_OPENSSL_COMPAT from autotests to compile time.  Further,
to improve code readability, a new NGX_QUIC_QUICTLS_API macro is
used for QuicTLS that provides old BoringSSL QUIC API.

This extends the target selection implemented in dad6ec3aa63f to support
Windows ARM64 platforms.  OpenSSL support for VC-WIN64-ARM target first
appeared in 1.1.1 and is present in all currently supported (3.x)
branches.

As a side effect, ARM64 Windows builds will get 16-byte alignment along
with the rest of non-x86 platforms.  This is safe, as malloc on 64-bit
Windows guarantees the fundamental alignment of allocations, 16 bytes.

Signed-off-by: Piotr Sikora <piotr@aviatrix.com>

With this change, the NGX_OPENSSL_NO_CONFIG macro is defined when nginx
is asked to build OpenSSL itself.  And with this macro automatic loading
of OpenSSL configuration (from the build directory) is prevented unless
the OPENSSL_CONF environment variable is explicitly set.

Note that not loading configuration is broken in OpenSSL 1.1.1 and 1.1.1a
(fixed in OpenSSL 1.1.1b, see https://github.com/openssl/openssl/issues/7350).
If nginx is used to compile these OpenSSL versions, configuring nginx with
NGX_OPENSSL_NO_CONFIG explicitly set to 0 might be used as a workaround.

To ensure proper target selection the NGX_MACHINE variable is now set
based on the MSVC compiler output, and the OpenSSL target is set based
on it.

This is not important as long as "no-asm" is used (as in misc/GNUmakefile
and win32 build instructions), but might be beneficial if someone is trying
to build OpenSSL with assembler code.

The change allows to compile QUIC with OpenSSL which lacks BoringSSL QUIC API.

This implementation does not support 0-RTT.

Threads are disabled during UNIX builds (see b329c0ab1a48), and also not
needed for Windows builds.

This used to be the default before OpenSSL 1.1.0.