multiqueue: Improve interleave calculation at startup and EOS

multiqueue: Improve interleave calculation at startup and EOS

* When a stream receives EOS, it will no longer change, we shouldn't take that
  stream into account for interleave calculation.

* When streams (re)appear, we do not want to grow the initial interleave values
  to excessive values. Instead of setting it to a default of 5s, progressively
  grow it to that maximum.

* When the status of input streams change (i.e. going to/from "some haven't
received data yet" and "all have received data"), update the interleave
immediately instead of waiting for (potentially) 5s of data before updating
it.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1892>