lttng: Add analysis requirements for LTTng UST Call Stack analysis

lttng: Add analysis requirements for LTTng UST Call Stack analysis

With this the user gets notified when the call stack analysis cannot be
executed. The help text will give some details about this.

Change-Id: Ib3628606a74ae5e83b60fde81720f7035d7eae86
Signed-off-by: Bernd Hufmann <Bernd.Hufmann@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/68235
Reviewed-by: Genevieve Bastien <gbastien+lttng@versatic.net>
Tested-by: Genevieve Bastien <gbastien+lttng@versatic.net>
Reviewed-by: Hudson CI
Reviewed-by: Bernd Hufmann <bernd.hufmann@ericsson.com>