Dynamic Table TTL

One limitation of the default_time_to_live option is that it only applies to newly inserted data so an expensive migration is required when altering the table-level TTL, which is not an uncommon request due to changes in retention policies.

This seems to have been a deliberate design decision when adding the Table TTL feature on CASSANDRA-3974, due to the reasons stated on this comment so we should revisit and potentially address these concerns.

I would like to explore supporting dynamic TTL, which would reflect any updates to the table-level default_time_to_live immediately to all table data.