Changes:

 * [`1d2e9e82`](cockroachdb/pebble@1d2e9e82) options: add EnableDeleteOnlyCompactionExcises Option

Release note: none.
Epic: none.

This change adds a cluster setting to be able to dynamically
disable excises in delete-only compactions. Excises allow
for range deletions / range key deletions to be applied to
sstables even if they don't fully overlap with the sstable;
we just produce virtual sstables for the remainder of the sstable.

Epic: none

Release note: None