QtSupport: Replace BaseQtVersion::clone()

... by a mechanism that doesn't require re-implementation in each
derived class.

A QtVersion's type() is uniquely defined by the supported type of
the factory creating it, so that factory can be found and used
for cloning. Non-base data is copied by a fromMap(toMap()) dance
as done in the project configurations.

As a side-effect, the *QtVersion copy constructors are not used
and not needed anymore.

Change-Id: I3aa5a0fd90a27dd115769e0573647cb5669641a0
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/android/androidqtversion.h

@@ -40,8 +40,6 @@ class AndroidQtVersion : public QtSupport::BaseQtVersion
 public:
     AndroidQtVersion();
 
-    AndroidQtVersion *clone() const override;
-    QString type() const override;
     bool isValid() const override;
     QString invalidReason() const override;