ci: add client -> example.com test

This commit adds a CI run step that uses the client test binary to
connect to https://example.com, validating the presented certificate
chain using the system default CA bundle. We do this with `NO_ECHO=1` to
avoid trying to write a non-HTTP request and asserting on an echoed
response.

.github/workflows/libssl.yaml

@@ -41,6 +41,7 @@ jobs:
 
       - run: make PROFILE=release test
       - run: make PROFILE=release integration
+      - run: NO_ECHO=1 target/client example.com 443 default
 
   valgrind:
     name: Valgrind