Add default tool tips to text marks

The default tool tip should describe the general purpose
of the mark which is displayed in the UI when no tool tip
is explicitly set for the text mark.

Change-Id: I27aff26cf0f3458d454428e805a9b323191dc393
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/plugins/debugger/breakhandler.cpp

@@ -896,6 +896,8 @@ BreakHandler::BreakHandler()
     qRegisterMetaType<BreakpointModelId>();
     TextEditor::TextMark::setCategoryColor(Constants::TEXT_MARK_CATEGORY_BREAKPOINT,
                                            Theme::Debugger_Breakpoint_TextMarkColor);
+    TextEditor::TextMark::setDefaultToolTip(Constants::TEXT_MARK_CATEGORY_BREAKPOINT,
+                                            tr("Breakpoint"));
 
 #if USE_BREAK_MODEL_TEST
     new ModelTest(this, 0);