Unification and/or feature parity for TextInput/TextField and TextEdit/TextArea

TextInput is a single-line plain text editor, while TextEdit is a multi-line rich text editor. They are inherited by TextField and TextArea respectively

There is lots of duplicated functionality between them (e.g. the `activeFocusOnPress` property and the `editingFinished()` signal), but some functionality is only available in one of them even though it makes sense to be in both (e.g. `textEdited()` signal)

Suggestions

• Short-term: Go through the API of both "branches" of types and ensure that all sensible properties/signals/methods are available in both.
• Long-term: Make both TextInput and TextEdit share a common ancestor to avoid duplicating properties/signals/methods.
• Long-term: Where sensible, move properties/signals/methods from the Qt Quick Controls child to the Qt Quick parent (e.g. the `pressed(MousEvent)` and `released(MousEvent)` signals).