Add information about defered properties to qmltypes

Deferred properties are used in a few places already, most notably in Controls. With the work in QTBUG-95117, they will only become more prevalent.

To have good support for them in tooling, we need to store information about them in the qmltypes files.

Things to note:

• you can defer properties defined outside of the class (in the parent, child classes, probably attached properties)
• With QTBUG-95117, there might be  a difference between no entry at all, and an entry containing the empty string