adaptivedemux: Don't calculate bitrate for header/index fragments

They are generally substantially smaller than regular fragments, and therefore we end up pushing totally wrong bitrates downstream.

Fixes erratic buffering issues with DASH introduced by 66f5e874

added Regression label

assigned to @gstreamer-merge-bot

added 1.18 Needs backport labels

mentioned in commit bilboed/gst-plugins-bad@9fec99f5

added 6 commits

• 5089fc34...5578e76e - 5 commits from branch gstreamer:master
• 9fec99f5 - adaptivedemux: Don't calculate bitrate for header/index fragments

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assigned to @bilboed and unassigned @gstreamer-merge-bot

I couldn't merge this branch: CI failed!

added 14 commits

• 9fec99f5...3a554f6d - 13 commits from branch gstreamer:master
• e543caee - adaptivedemux: Don't calculate bitrate for header/index fragments

Compare with previous version

assigned to @gstreamer-merge-bot and unassigned @bilboed

mentioned in commit bilboed/gst-plugins-bad@88721944

added 3 commits

• e543caee...1246b448 - 2 commits from branch gstreamer:master
• 88721944 - adaptivedemux: Don't calculate bitrate for header/index fragments

Compare with previous version

assigned to @bilboed and unassigned @gstreamer-merge-bot

I couldn't merge this branch: CI failed!

unassigned @bilboed

assigned to @gstreamer-merge-bot

assigned to @bilboed and unassigned @gstreamer-merge-bot

I couldn't merge this branch: CI failed!

assigned to @gstreamer-merge-bot and unassigned @bilboed

stupid ci ...

assigned to @bilboed and unassigned @gstreamer-merge-bot