[Hopper CuTeDSL] Add grouped GEMM persistent kernel and tests (#3091)

Implement grouped GEMM (C_g = A_g x B_g for g groups) on Hopper using
CuTe DSL, extending the dense persistent GEMM with per-group TMA
descriptor management.

Kernel design (grouped_gemm.py):
- Warp-specialized pipeline: DMA warp group handles TMA loads and
  per-group tensormap updates; MMA warp group runs WGMMA and stores C
- StaticPersistentGroupTileScheduler for cross-group tile scheduling
- Per-group TMA descriptor updates via GMEM or SMEM mode
- Supports fp16, fp8 (E4M3FN/E5M2), int8 with mixed A/B dtypes
- Configurable tile shapes (128x128, 128x256) and cluster shapes
- Fix base TensorMapManager: hoist uniform_smem_ptrs outside predicated
  block to avoid illegal @P0 R2UR on sm_90a

Tests (test/examples/CuTeDSL/hopper/test_grouped_gemm.py):
- L0 compile and L1 correctness pytest suite covering tile shapes,
  dtypes, major modes, cluster shapes, group counts, and mixed sizes
- Move to test/examples/CuTeDSL/hopper/ following sm_100a convention
- Fix deprecated startdir arg in test_sharding.py pytest hook

test/utils/test_sharding.py

@@ -495,7 +495,7 @@ def pytest_runtest_makereport(item, call):
                             report.longrepr = f"Expect exception '{xfail_info}', but got '{type(call.excinfo.value)}'"
 
 
-def pytest_report_collectionfinish(config, start_path, startdir, items):
+def pytest_report_collectionfinish(config, start_path, items):
     if not config.getoption("--collect-only"):
         return