mxfdemux: Handle files produced by legacy FFmpeg

mxfdemux: Handle files produced by legacy FFmpeg

Until March 2022, the FFmpeg MXF muxer would write the various index table
segments with the same instance ID, which should only be used if it is a
duplicate/repeated table.

In order to cope with those, we first compare the other index table segment
properties (body/index SID, start position) before comparing the instance
ID. This will ensure that we don't consider them as duplicate, but can still
detect "real" duplicates (which would have the same other properties).

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2407>