GHA: refactor mingw UTs and add missing tls_crypt

GHA: refactor mingw UTs and add missing tls_crypt

I thought instead about moving this into a loop inside
powershell. But then error handling becomes annoying.
So let's GitHub handle it.

Change-Id: I9831f352c07b5c58a4e2d6a3dd5417842e0887d2
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <20230718105233.620193-1-frank@lichtenheld.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg26868.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>