GPU pipeline reorganization

[adam-smnk]

Cleans up and simplifies GPU pipeline in preparation for unified vector based lowering.

The main goal is to retire old experimental paths and prepare for more common vendor-agnostic lowering infrastructure. It is another step toward GPU codegen through vectorization.

Summary of changes:

• moves to tiling based kernel outlining - retires naive outlining based on Linalg to parallel loops conversion
• retires packed GEMM GPU kernels - currently irrelevant for GPU kernel creation
• retires custom Linalg to WMMA lowering - to be replaced with generic vectorization scheme in the future
• cleanups tests and adjusts existing ones to pipeline changes
• allows to override default GPU tiling sizes and to use tile setting provided by DLTI (for now uses CPU tile size)

[adam-smnk]

As with the previous GPU cleanup, a quick sanity check should be enough. 🙂

[adam-smnk]

Rebase on main plus removed small unused leftovers.