clutter: Pass events to pointer a11y before going through filters

We want all pointer events to be passed through the pointer a11y processing before going through event filters: Once we go through event filters, events might be dispatched to Wayland and get filtered out.

With the changes to immediately dispatch events to wayland, this changed and the pointer a11y is now no longer seeing any events going to wayland clients. Fix it by shuffling things around a bit and letting pointer a11y take a peek at events earlier.

Fixes: gnome-shell#5192 (closed)