ss: remove linear component from node search.

ss: remove linear component from node search.

Before, nodes had their intervals only sorted by end times,
which meant finding the first interval which started later
than time t implied a binary search for any interval ending
at time t, then a linear iteration to the first interval
ending before (inclusively) t.
We remove this component by ordering intervals by end times
then by start times, so that the binary search can directly
return the first interval ending before (inclusively) t.

Change-Id: I3e4fd02880d56360fc082023c08b92f8a6e4350e
Signed-off-by: Loïc Prieur-Drevon <loic.prieurdrevon@gmail.com>
Reviewed-on: https://git.eclipse.org/r/86865
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-by: Hudson CI
Reviewed-by: Alexandre Montplaisir <alexmonthy@efficios.com>
Tested-by: Alexandre Montplaisir <alexmonthy@efficios.com>