effects/glide: Adjust the effect to projection matrix changes

With per-screen rendering, the projection matrix is no longer created
with the workspace geometry, i.e. all screen geometries united, so the
center of the workspace geometry may not map to (0, 0) in the clip
coordinates.

GLRenderTarget::virtualScreenGeometry() can be used to query the rect
that was used to create the projection matrix.

BUG: 442770


(cherry picked from commit c29c437e)