fix ChunkedDataReader chunked + gzip decomp: if reading one chunk yields no data
(due to more data being needed for gzip decomp), keep reading more blocks until there is data
or last block is reached (or error). Ensure a single read() call will return some data if there is any
when given a redis path of redis://<host>/<db>/<key>, use <key> as a
sorted cdx file with zrangebylex!

modified tests but need zrangebylex() support in fakeredis to finish
cdx redis: disable new test until fakeredis supports zrangebylex()