message: Move region mappings outside of unsafe
diff: @@ -73,13 +73,9 @@ impl ReadonlyStorage for ExternalStorage {
  // See: https://github.com/CosmWasm/cosmwasm/pull/509
  let start_region = start.map(build_region);
  let end_region = end.map(build_region);
  - let iterator_id = unsafe {
  - db_scan(
  - start_region.as_ref().map(get_region_address).unwrap_or(0),
  - end_region.as_ref().map(get_region_address).unwrap_or(0),
  - order as i32,
  - )
  - };
  + let start_region = start_region.as_ref().map(get_region_address).unwrap_or(0);
  + let end_region = end_region.as_ref().map(get_region_address).unwrap_or(0);
  + let iterator_id = unsafe { db_scan(start_region, end_region, order as i32) };
  let iter = ExternalIterator { iterator_id };
  Box::new(iter)
  }
  