feat(gzip): switch to zlib-rs for default gz backend

[digizeph]

Preliminary benchmark shows significant performance boost by switching to zlib-rs.

gzip_decompress/flate2_gz_decode
                        time:   [2.7369 µs 2.7461 µs 2.7550 µs]
                        thrpt:  [21.116 MiB/s 21.184 MiB/s 21.255 MiB/s]
                 change:
                        time:   [-43.284% -42.934% -42.605%] (p = 0.00 < 0.05)
                        thrpt:  [+74.230% +75.236% +76.316%]
                        Performance has improved.