Add zoom and rotation to PdfMultiPageView

Currently, scaleToWidth() and scaleToPage() choose the scale of the
first page to fit the given viewport size, and as long as all pages are
the same size, it works.  On the other hand, the PinchHandler only
affects the scale of the page on which the pinch gesture occurs.
Calling resetScale(), scaleToWidth() or scaleToPage() undoes the
effect of any previous pinch gesture or any other kind of scaling change.

Task-number: QTBUG-77513
Change-Id: Ia3227ca9c4af263eb8505dbd6336657984c66ab0
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>