videorate: Add a `max-closing-segment-duplication-duration` property

This allows users to let videorate fully fill the segments when received EOS or on new segment, removing an arbitrary limit of 25 duplicates which might not be what the user wants (for example on low FPS stream in GES, that sometimes leaded to broken behavior)

Also refactor a bit the code so the conditions are simpler to read, adding the condition on top of what we had would have become even more complicated.