Table truncate command

Add truncate operation i.e. delete all contents of table, without removing table config and schema.

For offline, this simply means deleting all segments (everything a delete operation does, but keep the table/schema definition)
For realtime, this means deleting all segments, both completed and consuming. Then, we should recreate the ideal state, just like we would've for a new realtime table.

Start by locating the existing delete operation and the code paths for offline and realtime tables, especially where completed and consuming segments are handled. Confirm how a new realtime table's ideal state is created; done means truncation removes all data while preserving the table configuration and schema, including recreating the realtime ideal state.

Written by the indexing model from the issue text.