feat: add per-head fp8 kv attention calibration

[zeel2104]

Description

Adds per-head FP8 KV/attention calibration support on top of the existing per-tensor static FP8 paths.

Main changes:

• Adds static_kv_granularity and static_attention_granularity options with "tensor" as the default and "head" as the new per-head mode.
• Collects per-head k_scale, v_scale, and q_scale for attention tensors shaped as [batch, heads, seq, head_dim].
• Exports LLMC metadata with attn_head strategy for per-head KV/attention scales.
• Preserves existing per-tensor behavior by default.
• Adds tests for helper MHA/GQA scale shapes, LLMC export, and AutoRound export.
• Fixes a Windows-only test file-lock issue by closing safe_open handles before reusing the output path.

Type of Change

New feature

Related Issues

Relates to #2026

Checklist Before Submitting

• My code has been tested locally.
• Documentation has been updated as needed.
• New or updated tests are included where applicable.
• The CUDA CI has passed. You can trigger it by commenting /azp run Unit-Test-CUDA-AutoRound.

Tested locally:

• python -m pytest test/test_cpu/test_experimental_fp8_granularity.py -q
• python -m pytest test/test_cpu/export/test_llmc_format.py -q
• python -m pytest test/test_cpu/export/test_export.py -k "per_head or static_afp8_export or static_fp8_attn" -q
• python -m pytest test/test_cpu/quantization/test_mxfp_nvfp.py -k "fp8_kv_attn" -q

Note:

• test/test_cpu/integrations/test_inc_integration.py was not run because neural_compressor is not installed locally.

[zeel2104]

/azp run Unit-Test-CUDA-AutoRound

[azure-pipelines]

Commenter does not have sufficient privileges for PR 2044 in repo intel/auto-round

[yiliu30]

/azp run Unit-Test-CUDA-AutoRound

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[yiliu30]

/azp run Unit-Test-CUDA-AutoRound

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).