Add tests for finding certificates in Windows cert store

Add tests for finding certificates in Windows cert store

- find_certificate_in_store tested using 'SUBJ:', 'THUMB:'
  and 'ISSUER:' select strings. Uses test certificates
  imported into the store during the import test.

Change-Id: Ib5138465e6228538af592ca98b3d877277355f59
Signed-off-by: Selva Nair <selva.nair@gmail.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20230315013516.1256700-3-selva.nair@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg26415.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>