WL_OUTPUT_TRANSFORM refactoring

Some follow up work stemming from !1015 (comment 1656682)

I'll just copy and paste Pekka's comment from there to here:

Refactor weston_output_update_matrix() and move the switch-case-ladders handling enum wl_output_transform into matrix.c. Use that helper from weston_output_update_matrix() obviously. Then delete the similar ladders from weston_surface_build_buffer_matrix() and make that use the helper as well with a matrix inversion added.

Then, if we still have more of those ladders open-coded (clients/simple-damage?), migrate those as well.

And make something for all the open-coded "get width/height" simple cases that switch on enum wl_output_transform as well.