Debugger: Extend use of Dumper.putPlotData

Make backend-agnostic and use it for QFiniteStack and
std::{array,vector}

Change-Id: I1702d4290ee24c957f77b539591313ac83021003
Reviewed-by: hjk <hjk121@nokiamail.com>
Debugger: Add context menu option to save stack as *.tasks file.

The task files can be attached to bug reports and then conveniently
loaded into the build issues pane for later investigation.

Change-Id: I463de957bf545ab89f630ab108f92cc253d81fa5
Reviewed-by: hjk <hjk121@nokiamail.com>