[ET-VK] Making stride equals dilation the default mode for conv2d dw. (#7629)

* [ET-VK] Fixing conv2d dw incorrect output when stride != dilation issue.

Pull Request resolved: https://github.com/pytorch/executorch/pull/7595

This diff moves current implementation of conv2d dw as a special case when stride equals dilation in the Vulkan backend of Executorch, since that's the only time this kind of caching is possible.

If stride does not equal dilation the old implementation is used.

Additional test cases are added to ensure computation is correct when stride != dilation.
ghstack-source-id: 261183385
@exported-using-ghexport

Differential Revision: [D67908916](https://our.internmc.facebook.com/intern/diff/D67908916/)

* [ET-VK] Making stride equals dilation the default mode for conv2d dw.

Pull Request resolved: https://github.com/pytorch/executorch/pull/7596

This diff makes changes make stride equals dilation the default mode for conv2d dw output op.
Adds a different source file to handle stride not equal dilation case.
ghstack-source-id: 261183386

Differential Revision: [D67979760](https://our.internmc.facebook.com/intern/diff/D67979760/)

* Update conv2d_dw_output_tile.glsl

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Co-authored-by: Vivek Trivedi <5340687+trivedivivek@users.noreply.github.com>