message: blobcache: avoid unnecessary digest check when bitmap indicated non-downloaded chunk
  With shared chunk bitmap applied, we don't have try to recover blobcache
  as principle is that chunk bitmap is trusted. The chunk must not be downloaded before.
  Avoid calculating such digest can help save cpu cycles and reduce latency
diff: @@ -202,7 +202,10 @@ impl BlobCache {
  // Try to recover cache from blobcache first
  // For gzip, we can only trust ready blobcache because we cannot validate chunks due to
  // stargz format limitations (missing chunk level digest)
  - if (self.compressor() != compress::Algorithm::GZip || has_ready)
  + // With shared chunk bitmap applied, we don't have try to recover blobcache
  + // as principle is that chunk bitmap is trusted. The chunk must not be downloaded before.
  + if (self.compressor() != compress::Algorithm::GZip && !blob.with_extended_blob_table()
  + || has_ready)
  && self
  .read_blobcache_chunk(fd, chunk, one_chunk_buf, !has_ready || self.need_validate())
  .is_ok()
  