fix(handlers): improve gzip reader according to recent changes in cpython.

The gzip._GzipReader we're inheriting from had some changes to stay up
to date with changes in zlib library and to perform some optimization.

Specifically:

- GzipFile.read has been optimized. There is no longer a unconsumed_tail
  member to write back to padded file. This is instead handled by the
  ZlibDecompressor itself, which has an internal buffer.
- _add_read_data has been inlined, as it was just two calls.

We've adapted our own code to reflect these changes.

More info: python/cpython#97664

Author: qkaiser

unblob/handlers/compression/_gzip_reader.py

@@ -1,4 +1,5 @@
 import gzip
+import zlib
 
 from ...file_utils import DEFAULT_BUFSIZE
 
@@ -10,14 +11,19 @@ def read_header(self):
         self._init_read()
         return self._read_gzip_header()
 
+    def _add_read_data(self, data):
+        self._crc = zlib.crc32(data, self._crc)
+        self._stream_size = self._stream_size + len(data)
+
     def read(self):
         uncompress = b""
 
         while True:
             buf = self._fp.read(DEFAULT_BUFSIZE)
 
             uncompress = self._decompressor.decompress(buf, DEFAULT_BUFSIZE)
-            self._fp.prepend(self._decompressor.unconsumed_tail)
+            if hasattr(self._decompressor, "unconsumed_tail"):
+                self._fp.prepend(self._decompressor.unconsumed_tail)
             self._fp.prepend(self._decompressor.unused_data)
 
             if uncompress != b"":