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/projectexplorer/projectwindow.cpp

@@ -206,7 +206,9 @@ void BuildSystemOutputWindow::updateFilter()
                            m_filterActionCaseSensitive.isChecked() ? Qt::CaseSensitive
                                                                     : Qt::CaseInsensitive,
                            m_filterActionRegexp.isChecked(),
-                           m_invertFilterAction.isChecked());
+                           m_invertFilterAction.isChecked(),
+                           0 /* before context */,
+                           0 /* after context */);
 }
 
 class VanishedTargetPanelItem : public TreeItem