Using WINHTTP_AUTOPROXY_ALLOW_AUTOCONFIG on Windows versions older than Windows 10 1703 (build 15063)
is not supported and causes WinHttpGetProxyForUrl to fail with ERROR_INVALID_PARAMETER. This results in failures
reaching the control on environments where a proxy is required.
We use wingoes version detection to conditionally set the WINHTTP_AUTOPROXY_ALLOW_AUTOCONFIG flag
on Windows builds greater than 15063.
While there, we also update proxy detection to use WINHTTP_AUTO_DETECT_TYPE_DNS_A, as DNS-based proxy discovery
might be required with Active Directory and in certain other environments.
Updates tailscale/corp#29168
Fixes#879
Signed-off-by: Nick Khyl <nickk@tailscale.com>
191afd3390