#### Problem
RocksDB's delete_range applies to [from, to) while delete_file_in_range
applies to [from, to] by default, and the rust-rocksdb api does not include
the option to make delete_file_in_range apply to [from, to). Such inconsistency
might cause `blockstore::run_purge` to produce an inconsistent result as it
invokes both delete_range and delete_file_in_range.
#### Summary of Changes
This PR makes all our purge / delete related functions to be inclusive
on both starting and ending slots.
6d070cee08