* MySQL 5.7 and MySQL 8.0 need different percona-xtrabackup package version.
Added Percona XtraBackup 8 support for MySQL 8.x backup and restore.
* Construct different backup container image names for MySQL 5.7 and MySQL 8.0
based on the default option value.
* Two docker images are uploaded for backup/restore:
openstacktrove/db-backup-mysql5.7:1.0.0 and
openstacktrove/db-backup-mysql8.0:1.0.0. Trove guest agent can automatically
choose the approriate one based on the datastore version.
* Added option "secure-file-priv=NULL" in MySQL config template to fix
https://github.com/docker-library/mysql/issues/541.
* Stop using IDENTIFIED BY in GRANT clause (also REVOKE). Starting with MySQL 8
creating a user implicitly using the GRANT command is not supported.
Story: #2008275
Task: #41143
Change-Id: Ibdec63324b1b39ba9b8a38dbe529da17bbb06767
d1af33f17b