[CoreML][iOS/MacOS] Add the CoreML executor (#64522)

[CoreML][iOS/MacOS] Add the CoreML executor (#64522)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/64522

The `PTMCoreMLExecutor` serves as a bridge between the delegate APIs and Core ML runtime.
ghstack-source-id: 138324217

allow-large-files

Test Plan:
iOS:
Run the CoreML tests in the playground app

MacOS:

```
buck test pp-macos

PASS     633ms  1 Passed   0 Skipped   0 Failed   CoreMLTests
```

{F657776101}

Reviewed By: raziel, iseeyuan

Differential Revision: D30594042

fbshipit-source-id: a42a5307a24c2f364333829f3a84f7b9a51e1b3e