AutoTest: Add ability to limit test description

Test description is made of entire test output,
and if it is very big it can heavily limit
test output pane usability.
This commit adds option to limit description size.

Change-Id: I5aae5e460f1939cd94a84ab1ca79f413d66d8bf2
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/autotest/testsettings.h

@@ -55,6 +55,8 @@ struct TestSettings
     bool omitInternalMssg = true;
     bool omitRunConfigWarn = false;
     bool limitResultOutput = true;
+    bool limitResultDescription = false;
+    int resultDescriptionMaxSize = 10;
     bool autoScroll = true;
     bool processArgs = false;
     bool displayApplication = false;