[ExecuTorch][WebGPU] SDPA test suite: replay + dynamic input_pos + in-graph KV cache (#20260)

This PR was created by the merge bot to help merge the original PR into
the main branch.
ghstack PR number: #20087 by
@JulianCloudNTH
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ghstack PR base:
https://github.com/pytorch/executorch/tree/gh/JulianCloudNTH/20/base
ghstack PR head:
https://github.com/pytorch/executorch/tree/gh/JulianCloudNTH/20/head
Merge bot PR base:
https://github.com/pytorch/executorch/tree/gh/JulianCloudNTH/19/orig
Merge bot PR head:
https://github.com/pytorch/executorch/tree/gh/JulianCloudNTH/20/orig

@diff-train-skip-merge

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Co-authored-by: Julian Ng-Thow-Hing <juliannth@meta.com>

Author: pytorchbot