Fix Metal codegen for functions using sk_Vertex/InstanceID.

We now have dedicated Requirements bits for these values and pass
them to helpers as necessary.

Bug: skia:14609
Change-Id: I3ec898efac1e5dd439b463182b9302c7f82a7715
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/720915
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
12 files changed