Changes

tmf.ui: Don't draw arrows that cannot be displayed in TimeGraph

A arrow can only be displayed if its source is visible, its destination
is visible, or the source and destination are on opposite sides of the
visible area.

On a typical workspace of 2560 x 1440, with a trace compass trace,
the number of arrows drawn drops by an average of 95%.

[Changed] Don't draw arrows that cannot be seen

Change-Id: I7b7dea8575e07e47a850f13aec25e6ace9173d5c
Signed-off-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/c/tracecompass/org.eclipse.tracecompass/+/201712
Tested-by: Patrick Tasse <patrick.tasse@gmail.com>
Tested-by: Trace Compass Bot <tracecompass-bot@eclipse.org>
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>