debug timer can be painted ober by quad glyphs

[Ivan Avdeev]

This is due to the fixed render order: quads are rendered after grid, and render timer is a part of grid. But render timer is generated only after all regular cells are updated and quad list is already updated.

There's no easy fix:

• changing render order is infeasible. Grid passes draw background.
• adding a separate pass just for render timer is weird
• clipping cells that fall within debug timer is also weird, and might also have small perf impact given the idiosyncratic mechanism of how internal cells are passed to the rendering