alternator: Include LatestStreamLabel in resulting desc for create/update table
alternator: Include LatestStreamLabel in resulting desc for create/update table

Fixes #7162

Same value as 'StreamLabel' in the currently active stream (cdc log) if
enabled.

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla