WL#9091: Remove --ssl, --ssl-verify-server-cert client-side options

WL#8785 implemented the --ssl-mode client option, which incorporated the 
functionality of the --ssl and --ssl-verify-server-cert client options. 
Consequently, --ssl and --ssl-verify-server-cert were deprecated in 5.7.

Similarly, WL#8785 implemented the MYSQL_OPT_SSL_MODE option for the 
mysql_options() C API function. This option incorporates the functionality of the 
MYSQL_OPT_SSL_ENFORCE and MYSQL_OPT_SSL_VERIFY_SERVER_CERT, which were deprecated 
in 5.7.

This task shall remove the --ssl and --ssl-verify-server-cert client options in 
5.8. This includes removal of --ssl synonyms such as --skip-ssl. (The server-side 
--ssl option remains unchanged.)

This task shall also remove MYSQL_OPT_SSL_ENFORCE and 
MYSQL_OPT_SSL_VERIFY_SERVER_CERT.