ClangCodeModel: Try to find help items for method overrides

... in the base class.
This is purely a heuristic, but should work well for Qt-based user
projects.

Fixes: QTCREATORBUG-9845
Change-Id: Icca336b3568c2c5f07a9eaf6a183bf6c7c4275bd
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clangdclient.h

@@ -69,6 +69,9 @@ public:
     void gatherHelpItemForTooltip(
             const LanguageServerProtocol::HoverRequest::Response &hoverResponse,
             const LanguageServerProtocol::DocumentUri &uri);
+    bool gatherMemberFunctionOverrideHelpItemForTooltip(
+            const LanguageServerProtocol::MessageId &token,
+            const QList<ClangdAstNode> &path);
 
     void setVirtualRanges(const Utils::FilePath &filePath,
                           const QList<LanguageServerProtocol::Range> &ranges, int revision);