[LLVMGPU] Add sm_120 TileAndFuse config coverage, consolidate MMA sync pipeline tests (#24577)

## Description
Adds LLVMGPU TileAndFuse config-selection coverage for the CUDA `sm_120`
target and consolidates MMA sync pipeline-lowering coverage across
NVIDIA
GPU architectures.

The `sm_120` config-selection test verifies that f16 matmul cases select
the
NVIDIA MMA TileAndFuse path before any architecture-specific tuning is
introduced. The pipeline-lowering tests are kept target-independent
because
they start from IR with an attached `mma_sync` intrinsic and only verify
that
the selected lowering pipeline generates the corresponding
`nvgpu.mma.sync`
ops.

Covered `sm_120` config-selection cases:
- `f16xf16 -> f32` matmul selects TileAndFuse with `NV_MMA_SYNC`
- `f16xf16 -> f16` matmul selects TileAndFuse with `NV_MMA_SYNC`
- `f16xf16 -> f32` matmul accumulate sets `convert_acc_gemm`

Covered target-independent pipeline-lowering cases:
- `f16xf16 -> f32` TileAndFuse lowering generates `nvgpu.mma.sync`
- `f16xf16 -> f16` TileAndFuse lowering generates `nvgpu.mma.sync`
- `f16xf16 -> f32` VectorDistribute lowering generates `nvgpu.mma.sync`
- `f16xf16 -> f16` VectorDistribute lowering generates `nvgpu.mma.sync`

This is baseline regression coverage only; it does not introduce new
tile
heuristics or `sm_120`-specific tuning.

## Test
- `llvm-lit -v \

compiler/src/iree/compiler/Codegen/LLVMGPU/test/NVVM/config_tile_and_fuse_sm120.mlir
\

compiler/src/iree/compiler/Codegen/LLVMGPU/test/NVVM/config_tile_and_fuse_sm80.mlir
\

compiler/src/iree/compiler/Codegen/LLVMGPU/test/NVVM/pipeline_tile_and_fuse_mma_sync.mlir
\

compiler/src/iree/compiler/Codegen/LLVMGPU/test/NVVM/pipeline_vector_distribute_mma_sync.mlir`


```
-- Testing: 4 tests, 4 workers --
PASS: IREE :: src/iree/compiler/Codegen/LLVMGPU/test/NVVM/config_tile_and_fuse_sm120.mlir (1 of 4)
PASS: IREE :: src/iree/compiler/Codegen/LLVMGPU/test/NVVM/config_tile_and_fuse_sm80.mlir (2 of 4)
PASS: IREE :: src/iree/compiler/Codegen/LLVMGPU/test/NVVM/pipeline_vector_distribute_mma_sync.mlir (3 of 4)
PASS: IREE :: src/iree/compiler/Codegen/LLVMGPU/test/NVVM/pipeline_tile_and_fuse_mma_sync.mlir (4 of 4)

Testing Time: 0.14s

Total Discovered Tests: 4
  Passed: 4 (100.00%)
```

---------

Signed-off-by: weimin023 <tnwilly@gmail.com>