vcpkg: switch to manifest

vcpkg: switch to manifest

Add vcpkg manifest file which lists
dependencies and enable manifest usage in
project file.

This simplifies build process by eliminating
separate "vcpkg install" step to install dependencies.

Since vcpkg added openssl3 port, remove ours.

Signed-off-by: Lev Stipakov <lev@openvpn.net>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20220505121449.347-1-lstipakov@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg24285.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>