Add a workload with tablets-enabled post rolling-upgrade from a tablets-disabled version

[yarongilor]

[A followup of: https://github.com//pull/7295#discussion_r1705439984]

Currently a migration from vnodes to tablets is not implemented (no alter table from tablets-disabled to enabled).
Hence the rolling-upgrade test can only enable tablets on an upgrade to a scylla version like 6.0/2024.1. The tablets will not really be used since user keyspaces will keep running with vnodes.
In order to validate tablets are operational post such an upgrade scenario, we can consider adding the following actions post rolling-upgrade:
create a keyspace with tablets-enabled.
run some workload and validate data.
(Another alternative could be restoring a table backup to a tablets-enabled keyspace)