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>