[ET-VK] Change weight packing in embedding

Pull Request resolved: https://github.com/pytorch/executorch/pull/7063

The existing weight tensor for aten.embedding is created using a `tensor_like` from the output tensor, which defaults to channel packed.

However, the weight tensor is actually a 2D-tensor of `(num_embedding, dim_of_embedding)`. It is better in space to use either width or height packing.

This diff changes the implementation to use height-packing.
ghstack-source-id: 255439082

Differential Revision: [D66421366](https://our.internmc.facebook.com/intern/diff/D66421366/)

Co-authored-by: Justin Yip <yipjustin@fb.com>