Address issue #1562 and fix a possible metrics naming issue (for Prometheus/Victoria integration)

[yabinmeng]

1. session identifier: use a random UUID string as the default value unless being explicitly overridden by the CLI "--session-name" option
2. for named scenario, if an alias is explicitly specified, make sure it is sanitized properly
3. for non-named scenario, currently the fullworkload file path will be part of the metrics names, sanitize the file path before adding them in the metrics names