Move QTextControl and QLineControl to the qtdeclarative repo

QTextControl is no longer shared between QTextEdit and QQuickTextEdit, and QLineControl is also exclusively used by QQuickTextInput. It doesn't make logistical sense to have these private class residing in qtbase when they're only used by qtdeclarative so they should be moved.

Ultimately QLineControl should probably also be integrated directly into QQuickTextInput as there isn't a clear division of responsibility between the classes and the overhead of coordinating the two classes is not insignificant.