[REQUEST] Update example_walker.py to use tile API

[shi-eric]

Description

wp.matmul() will eventually be removed, so we want to make sure this example uses the tile programming model.

[shi-eric]

BTW, one complication is that the tile API doesn't work with CUDA 11 builds due to the use of nvJitLink...

[daedalus5]

Yeah that is a complication. Possibly will be an issue with automated testing? Is it possible to filter example tests by required CUDA version? Although we have other examples now that use the Tile API, so I guess it's no different.

This just means we don't directly support matrix multiplication unless you're running CUDA 12+ after the deprecation.

[shi-eric]

There's also a usage of wp.matmul() in the linear solvers module.

[gdaviet]

Yes, wp.matmul is currently used as the default dense matrix-vector multiplication algorithm for the iterative linear solvers. A tile-based alternative should be possible, and I don't believe the linear solvers are part of the officially supported API, so limiting support to cuda 12 might be an option.