Core: Show context of filter matches

When inspecting logs often enough the relevant information is next to
the line with the unique expression that's easy to match. The `grep`
tool solves this problem by providing various `--*context` options
which configure how much context to show for each match.

This change tries to replicate this feature.

Task-number: QTCREATORBUG-30167
Change-Id: I6432870c0b958df8c5dc616009aea4ca54973245
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/coreplugin/messageoutputwindow.cpp

@@ -99,10 +99,15 @@ bool MessageOutputWindow::canNavigate() const
     return false;
 }
 
+bool MessageOutputWindow::hasFilterContext() const
+{
+    return true;
+}
+
 void MessageOutputWindow::updateFilter()
 {
     m_widget->updateFilterProperties(filterText(), filterCaseSensitivity(), filterUsesRegexp(),
-                                     filterIsInverted());
+                                     filterIsInverted(), beforeContext(), afterContext());
 }
 
 } // namespace Internal