Changes

flame chart: Add a getEnd() method to IFlameChartProvider

This should return the end time of the analysis/state system underneath
and it will be used in the data provider to avoid having to wait for the
whole trace to be indexed before returning entries in case the trace
doesn't have a fast way to end time (like trace-event trace).

[Added] A IFlameChartProvider#getEnd method to return end time of the analysis

Change-Id: If3686a7b3fbf2b101b8aac2338fbf05a72980d32
Signed-off-by: Geneviève Bastien <gbastien+lttng@versatic.net>
Reviewed-on: https://git.eclipse.org/r/156015
Tested-by: Trace Compass Bot <tracecompass-bot@eclipse.org>
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>