More performant shadow

Shadows are not visible directly under the caster. This CL avoid drawing
shadows directly beneath the caster that's not visible to users.

Bug: 74062470
Test: Manual tests. Fps on Pixel3 (linux) dec from ~100-80ms to ~50-60ms. Also tested with FAB.
Change-Id: I3141b816f479e8ea486d0624ca00ddacd7b74acd
5 files changed