curl: SSH/SFTP connection reuse can bypass SSH key identity after ssh_config_matches removal

Summary: libcurl's SSH/SFTP connection reuse logic no longer binds a pooled SSH connection to the SSH key identity requested by the new transfer. After sshconfigmatches was removed, urlmatchprotoconfig again has no SSH-specific check for CURLOPTSSHPUBLICKEYFILE or CURLOPTSSHPRIVATEKEYFILE. An...