[TEST] Cover Gluon FP4 conversion ops

[Jokeren]

Summary

• Add CPU parity coverage for Gluon fp4_to_fp conversion on packed E2M1 input.

Validation

• PYTHONPATH=/mnt/keren/triton-viz pytest tests/end_to_end/test_gluon_fp4_to_fp_ops.py -q
• PYTHONPATH=/mnt/keren/triton-viz pytest tests/end_to_end/test_gluon_fp4_to_fp_ops.py tests/end_to_end/test_gluon_amd_scaled_upcast_ops.py tests/end_to_end/test_gluon_amd_wmma_ops.py tests/end_to_end/test_gluon_amd_buffer_ops.py tests/end_to_end/test_gluon_amd_cdna4_async_copy_ops.py tests/end_to_end/test_gluon_amd_tdm_ops.py tests/end_to_end/test_gluon_amd_core_helper_ops.py tests/end_to_end/test_gluon_libdevice_helper_ops.py tests/end_to_end/test_gluon_math_helper_ops.py tests/end_to_end/test_gluon_shared_memory_descriptor_ops.py tests/end_to_end/test_gluon_blackwell_tcgen05_multicast_ops.py tests/end_to_end/test_gluon_blackwell_tcgen05_two_cta_ops.py tests/end_to_end/test_gluon_blackwell_tensor_memory_reduction_ops.py tests/end_to_end/test_gluon_blackwell_tcgen05_copy_ops.py tests/end_to_end/test_gluon_blackwell_tcgen05_scaled_ops.py tests/end_to_end/test_gluon_blackwell_tcgen05_ops.py tests/end_to_end/test_gluon_blackwell_tensor_memory_ops.py tests/end_to_end/test_gluon_wgmma_ops.py tests/end_to_end/test_gluon_tma_im2col_ops.py tests/end_to_end/test_gluon_blackwell_tma_ops.py tests/end_to_end/test_gluon_tma_ops.py tests/end_to_end/test_gluon_async_copy_ops.py tests/end_to_end/test_gluon_core_ops.py tests/end_to_end/test_gluon.py tests/end_to_end/test_core.py tests/unit/test_adapters.py -q
• pre-commit run --files tests/end_to_end/test_gluon_fp4_to_fp_ops.py

[TEST] Cover Gluon FP4 conversion ops

PR chain

1. [TEST] Cover Gluon AMD WMMA ops #472
2. [TEST] Cover Gluon AMD scaled upcast ops #473
3. 👉 [TEST] Cover Gluon FP4 conversion ops #474 👈 YOU ARE HERE
4. [TEST] Cover Gluon AMD warp pipeline stages #475

⚠️⚠️ Please do not click the green "merge" button unless you know what
you're doing. This PR is part of a chain of PRs, and clicking the merge
button will not merge it into master. ⚠️⚠️