WIP: Add endpoint to get context info from timegraph trees

[bhufmann]

This can be used to get context info from a timegraph row, e.g. for critical path get hostId, threadId and thread name.

Requires:

• https://github.com/eclipse-tracecompass/org.eclipse.tracecompass/pull/52

Related changes:

• https://github.com/eclipse-cdt-cloud/tsp-typescript-client/pull/104
• https://github.com/eclipse-cdt-cloud/theia-trace-extension/pull/1065

Signed-off-by: Bernd Hufmann bernd.hufmann@ericsson.com