[webgpu] Optimize `Conv` by im2col-matmul #3

Job	Run time
6a. Build Regular (No Optional Features)	11m 8s
6b. Build Minimal (No Optional Features)	1s
6c. Build Extended Minimal (No Optional Features)	1s
2. Build Minimal (Exceptions Disabled)	11m 8s
1. Build Full ORT and Generate ORT Files	1s
4. Build Minimal (Globally Allowed Types)	1s
5. Build Extended Minimal	1s
3b. Build Minimal (Type Reduction)	1s
7. Build Extended Minimal (Android NNAPI)	1s
3a. Build Minimal (Custom Ops)	1s
	22m 24s

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