Metal: Remove autorelease use from libANGLE parts Use adoptObjCPtr() instead of AUTORELEASE to make all code uniform and more easy to reason about. Bug: angleproject:393263506 Change-Id: I15ea7e29784bcbe6bee6341fe288b340db813538 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6216870 Reviewed-by: Geoff Lang <geofflang@chromium.org> Auto-Submit: Kimmo Kinnunen <kkinnunen@apple.com> Commit-Queue: Kimmo Kinnunen <kkinnunen@apple.com> Reviewed-by: Alexey Knyazev <lexa.knyazev@gmail.com>