message: Fix get complete block header by height
  This commit uses the `completed_blocks` index rather than the available
  block range to fetch a complete block header by height in
  `read_complete_block_header_by_height`.
diff: @@ -1621,6 +1621,15 @@ impl Storage {
  if !(self.should_return_block(height, true)?) {
  return Ok(None);
  }
  + if self
  + .completed_blocks
  + .sequences()
  + .iter()
  + .find(|sequence| sequence.low() <= height && height <= sequence.high())
  + .is_none()
  + {
  + return Ok(None);
  + }
  res
  }
  