Investigate synchronous QWSI event delivery

The Wayland platform plugin is using the default QWSI delivery model, which is async, causing a delay between when an event comes in from the window server to when it's handled by Qt (as it has to wait for the next round of event processing to deliver the event).

Ideally events like mouse events, geometry changes, and expose/paint events are delivered synchronously, by using the <QWindowSystemInterface::SynchronousDelivery> template argument to the QWSI functions.

Doing so, especially for the geometry/expose/paint events will lead to a more predictable event flow for these critical code paths, and may also fix some glitches we're seeing today.