[xplat][metal] Add getters and setters for ivars in Conv2dOpContext (#57395)

[xplat][metal] Add getters and setters for ivars in Conv2dOpContext (#57395)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57395

As title
ghstack-source-id: 137223806

(Note: this ignores all push blocking failures!)

Test Plan:
### Lib Build
- `buck build caffe2:aten_metal_prepack`

### Integration Test
- `arc focus2 pp-ops -a ModelRunner`
- Click "Test Person/Hair Segmentation Model"

{F612831435}

- Image Classification Demo

{F614144868}

Reviewed By: xta0

Differential Revision: D28132020

fbshipit-source-id: 73560263a9d14e9ecfa39c69deb158a2ed8cb179