Don't reuse the same offset and size variables when reading
the byterange out of a MAP directive, as it can overwrite
values from a pending BYTERANGE directive for the next
fragment URI.
Fixes problems where the EXT-X-MAP directive has been written
into the playlist between an EXT-X-BYTERANGE and the fragment
URI it applies to.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/9533>
cdf1338e6b