[webgpu] Optimize `Conv` by im2col-matmul #5

Job	Run time
1. Build Full ORT and Generate ORT Files	1s
2. Build Minimal (Exceptions Disabled)	1s
6c. Build Extended Minimal (No Optional Features)	1s
4. Build Minimal (Globally Allowed Types)	1d 0h 0m 0s
6a. Build Regular (No Optional Features)	1s
5. Build Extended Minimal	1s
6b. Build Minimal (No Optional Features)	1s
3a. Build Minimal (Custom Ops)	0s
3b. Build Minimal (Type Reduction)	0s
7. Build Extended Minimal (Android NNAPI)	0s
	1d 0h 0m 6s

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