FindOpenSSL: Trust the user's OPENSSL_ROOT_DIR
When the user has specified the OpenSSL installation root directory, through the variable OPENSSL_ROOT_DIR or the environment variable with the same name, trust it, don't try to find OpenSSL anywhere else.
This is an alternative to !8463 (closed), hopefully more in line with received commentary: #18352 (comment 1361886)
Fixes: #18352 (closed)
Topic-rename: FindOpenSSL-trust-root-dir
Edited by Brad King