First step in running dEQP tests on the Metal backend on the bots

Bug: angleproject:4235
Change-Id: Ib191205179d98bc907cc7d48340744ea719a0bc2
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1978577Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Commit-Queue: Jonah Ryan-Davis <jonahr@google.com>