LanguageClient: generate issue pane entries for diagnostics

The clang code model already generated issue pane entries for received
diagnostics. Move the tracking of these issue pane entries to the
generic language client support and also generate entries for other
language servers.

Fixes: QTCREATORBUG-30549
Change-Id: I29f2ffbf199c3fdc5ca59a670f5033c833b96a49
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/languageclient/languageclientplugin.cpp

@@ -14,6 +14,8 @@
 #include <extensionsystem/iplugin.h>
 #include <extensionsystem/pluginmanager.h>
 
+#include <projectexplorer/taskhub.h>
+
 #include <QAction>
 #include <QMenu>
 
@@ -59,6 +61,11 @@ void LanguageClientPlugin::initialize()
     inspectAction.setText(Tr::tr("Inspect Language Clients..."));
     inspectAction.addToContainer(Core::Constants::M_TOOLS_DEBUG);
     inspectAction.addOnTriggered(this, &LanguageClientManager::showInspector);
+
+    ProjectExplorer::TaskHub::addCategory(
+                {Constants::TASK_CATEGORY_DIAGNOSTICS,
+                 Tr::tr("Language Server Diagnostics"),
+                 Tr::tr("Issues provided by the Language Server in the current document.")});
 }
 
 void LanguageClientPlugin::extensionsInitialized()