Metal: Use the per-context pipeline cache for RenderUtils The various RenderUtils classes created hundreds of RenderPipelineCache objects which did not reliquish their pipelines for the life of the Display. Hook them into the per-context PipelineCache so that they share the total pipeline limit with programs. Make RenderUtils fully RAII and store it in a unique_ptr in DisplayMtl. Remove RenderPipelineCache. Bug: chromium:1329376 Change-Id: I265e4e05fd3fd1da34932de36803cfe977f1f6a0 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4607153 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Quyen Le <lehoangquyen@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>