Add index.Tensor and aten.logical_not (#3221)

Summary:
Add missing llama ops for MPS delegate:
- `index.Tensor`
- `logical_not`

`index.put` works correctly for generating 1 token, but gives incorrect results on 2nd token. This remains disabled.

Summary of changes:
- Adds missing llama2 ops
- Adds support for launching Metal kernels instead of MPSGraph ops (if MPSGraph doesn't have the support)

cc cccclai , shoumikhin

Pull Request resolved: https://github.com/pytorch/executorch/pull/3221

Reviewed By: shoumikhin

Differential Revision: D56447710

Pulled By: cccclai

fbshipit-source-id: 778a485df5e67d1afd006b42f07b69c8a3961223