ClangTools: Query the tools for supported checks

...instead of hardcoding them for a particular version of
clang-tidy/clazy.

While at it, move also the tidy/clazy widgets to ClangTools as this
simplifies feeding data to them.

Reduce also the built-in configs to a single one using clang-tidy's and
clazy's default checks as they look very reasonable and saves us some
porting effort. Also, our previous built-in configs were just too
numerous.

Change-Id: Ib9297acb7810a940b86a23a8695530506a570394
Reviewed-by: Cristian Adam <cristian.adam@qt.io>

src/plugins/clangtools/settingswidget.h

@@ -41,9 +41,14 @@ class SettingsWidget : public QWidget
     Q_OBJECT
 
 public:
+    static SettingsWidget *instance();
+
     SettingsWidget(ClangToolsSettings *settings, QWidget *parent = nullptr);
     ~SettingsWidget() override;
 
+    QString clangTidyPath() const;
+    QString clazyStandalonePath() const;
+
     void apply();
 
 private: