storage: allow disabling value blocks via cluster setting

This will also require a change to Pebble, since value blocks are enabled for sstable formats >= TableFormatPebblev3.

In a production cluster, 1000s of versions of a single large k-v pair resulted in a > 100GiB range, and since we write a single sstable for the state machine during an incoming snapshot, we attempted to write a > 100GiB sstable that had to buffer the compressed values in memory, resulting in an OOM.

Jira issue: CRDB-40546