Drop the complex task scheduling logic for yarn.
Performance gains seen up to around ~30% FPS.

Bug: b/139142453
Change-Id: I264fee36323425a791088565d99dc586670a948a
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/35572Tested-by: Ben Clayton <bclayton@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>