Lazy load x86 import

[lucylq]

This is breaking executorch ci, see https://hud.pytorch.org/hud/pytorch/executorch/main/1?per_page=50&name_filter=unittest%20%2F%20macos

Error:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/Users/lfq/executorch/third-party/ao/torchao/testing/pt2e/utils.py", line 27, in <module>
    import torchao.quantization.pt2e.quantizer.x86_inductor_quantizer as xiq
  File "/Users/lfq/executorch/third-party/ao/torchao/quantization/pt2e/quantizer/x86_inductor_quantizer.py", line 1644, in <module>
    _register_quantization_weight_pack_pass()
  File "/Users/lfq/executorch/third-party/ao/torchao/quantization/pt2e/inductor_passes/x86.py", line 3221, in _register_quantization_weight_pack_pass
    if not torch.ops.mkldnn._is_mkldnn_acl_supported():
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/lfq/miniconda3/envs/executorch/lib/python3.12/site-packages/torch/_ops.py", line 1353, in __getattr__
    raise AttributeError(
AttributeError: '_OpNamespace' 'mkldnn' object has no attribute '_is_mkldnn_acl_supported'

Lazy load the x86 import, as macos doesnt have mkldnn

Test locally in executorch

(executorch) lfq@lfq-mac executorch % pytest --collect-only backends/xnnpack/test/quantizer/test_pt2e_quantization.py

[pytorch-bot]

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