Add a unit test for functions in cryptoapi.c

Add a unit test for functions in cryptoapi.c

- Though named cryptoapi_testdriver, right now this only tests
  parsing of thumbprint specified as a selector for --cryptioapicert
  option. More tests coming..

v2: a line that belongs here was mistakenly included in the previous
commit. Corrected.
v3: add to list of tests run in github actions
v4: - correct comment above invalid strings (copy paste error)
    - make invalid strings differ from correct value only in the
      explicitly introduced invalid characters/separators (one had
      two distinct errors which is not a robust test).

Signed-off-by: Selva Nair <selva.nair@gmail.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20230214200804.600405-1-selva.nair@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg26268.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>