ClangCodeModel: Provide tooltips via clangd

Note that we temporarily lose the ability to hover over an include and
get the full path of the header file. This is a valuable feature that we
need to restore, preferably by fixing clangd itself.
Fixing the remaining few test failures would likely require more
complicated code as well as additional LSP round-trips, and as of now
I'm not convinced it is worth the effort.

Change-Id: I08c72c4bd1268bbd67baeb57bbfd29d9b11303a5
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clanghoverhandler.cpp

@@ -26,6 +26,7 @@
 #include "clanghoverhandler.h"
 
 #include "clangeditordocumentprocessor.h"
+#include "clangmodelmanagersupport.h"
 
 #include <coreplugin/helpmanager.h>
 #include <cpptools/cppmodelmanager.h>
@@ -97,6 +98,12 @@ void ClangHoverHandler::identifyMatch(TextEditorWidget *editorWidget,
                                       int pos,
                                       BaseHoverHandler::ReportPriority report)
 {
+    if (ClangModelManagerSupport::instance()
+            ->clientForFile(editorWidget->textDocument()->filePath())) {
+        report(Priority_None);
+        return;
+    }
+
     // Reset
     m_futureWatcher.reset();
     m_cursorPosition = -1;