Finish LinalgExt operation support on all backends

[MaheshRavishankar]

One of the issues faced during SDXL support (#16854) was the missing support for operations added in LinalgExt on all codegen backends i.e, CPU, SPIRV and LLVMGPU.

Main Issues

1. iree_linalg_ext.attention https://github.com/openxla/iree/blob/2cdf1452bb2f877baf8723ab567363094bea10bd/compiler/src/iree/compiler/Dialect/LinalgExt/IR/LinalgExtOps.td#L514
   The main issue here was that the TileAndDecomposeAttentionPass is not really tested on any end-to-end compilation path. An efficient compilation of this op was built up using transform dialect script that was custom tuned for a single architecture. So it was hard to test models that had these operations on any other hardware.
2. iree_linalg_ext.winograd.input_transform
   https://github.com/openxla/iree/blob/2cdf1452bb2f877baf8723ab567363094bea10bd/compiler/src/iree/compiler/Dialect/LinalgExt/IR/LinalgExtOps.td#L1043
   This operation was working on SPIR-V backend and CPU backend, but not on the LLVMGPU backend. Again this wasnt tested end-to-end on all backends, but it was somewhat tested on CPU and SPIR-V backends (https://github.com/openxla/iree/blob/main/tests/e2e/linalg_ext_ops/winograd_input.mlir . So it was relatively easy to get working on LLVMGPU backend
3. iree_linalg_ext.winograd.filter_transform
   This operation actually does not exist. The filter transform for winograd was implemented by constant folding the weights and constant filters. To support this the filters for the convolution needed to be converted from resources to inline constants and were evaluated (very slowly) at compile time.
4. iree_linalg_ext.winograd.output_transform
   This operation was working on SPIR-V backend and CPU backend, but not on the LLVMGPU backend. Again this wasnt tested end-to-end on all backends, but it was somewhat tested on CPU and SPIR-V backends (https://github.com/openxla/iree/blob/main/tests/e2e/linalg_ext_ops/winograd_output.mlir . So it was relatively easy to get working on LLVMGPU backend

Covered commits

• a38e893
• 31effe9
• Unsubmitted change [Winograd] Improve thread distribution of winograd transform ops #16862

Immediate next steps

1. Make iree_linalg_ext.attention work on all backends (at least CPU and LLVMGPU backend) and have them tested in CI. They should be relatively functional on different architectures, which will make them robust and easily portable.
   • More in-tree end-to-end tests are needed to ensure op support. Even the modest testing of iree_linalg_ext.winograd.input_transform and iree_linalg_ext.winograd.output_transform on CPU and SPIR-V backend made it easy to port to LLVMGPU backend
   • The TileAndDecomposeAttentionPass needs to be fixed. This might require re-evaluating the pass implementation to use the PartialReductionTilingOpInterface
2. Adding an iree_linalg_ext.filter_transform operation to LinalgExt dialect.
   • Also need to make sure that the const_eval framework in IREE can pick up and fold away these operations.
3. Add more testing for the iree_linalg_ext.winograd.input_transform and iree_linalg_ext.winograd.output_transform ops by themselves as well as adding tests that convert a convolution into winograd and check that they work as a whole.