profiling: add wasd controls to flamegraphview

[arfio]

What it does

Fix issue #201 by using the context service already used by the timegraphview and the xyview.

How to test

1. Open a trace with a call stack analysis
2. Open the flamegraph view
3. Use the keys 'w', 'a', 's', 'd' to move in the view

Follow-ups

As the flamegraph view reuses a lot of the timegraph view code. Most of the code for this patch is copied from the timegraph implementation. Refactoring the timegraph view so that it is not coupled to a time based x-axis would fix that issue.

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the instructions in this template

[bhufmann]

It would be good to have some UI tests added to for this. There is already a SwtBot test for this view that could be used for that (see below). This could be done in a separate PR.

https://github.com/eclipse-tracecompass/org.eclipse.tracecompass/blob/master/analysis/org.eclipse.tracecompass.analysis.profiling.ui.swtbot.tests/src/org/eclipse/tracecompass/analysis/profiling/ui/swtbot/tests/flamegraph/FlameGraphTest2.java

[arfio]

I will be adding tests in a few days.