Inject for upsampling and coarsening operators

[swahtz]

📋 Originally created by @fwilliams

Original author: @fwilliams
Date: 2025-07-25T18:50:45Z

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Upsaming and pooling are using grid accessors which is bleh.

We should add a variant of inject that is aware of kernel size and stride for coarsening and upsampling grids.

We can update the pooling and upsampling operators to use this.

[fwilliams]

@sifakis did we do this? If not, we should