Add Metal backend type definitions and utilities

[manuelcandales]

Implement foundational types and utilities for Metal backend including:

• AOTI type aliases (AOTITensorHandle, AOTIRuntimeError, AOTITorchError)
• Device type handling functions
• Tensor storage size queries
• Tensor attribute utilities

[manuelcandales]

Stack from ghstack (oldest at bottom):

• Add Metal backend build system and runtime integration #15024
• Metal backend: Add operator implementations #15023
• Metal backend: Implement the AOTI MPS shim #15022
• Metal backend: Add AOTI shims for memory management #15021
• Add Metal backend core ETMetal runtime. #15020
• -> Add Metal backend type definitions and utilities #15019
• Add Metal backend Python preprocessing, partitioning, and tests #15015
• [ET][Metal] Update aoti_common with additional AOTI functions needed by Metal backend #15003

[pytorch-bot]

🔗 Helpful Links

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❌ 5 New Failures, 3 Pending

As of commit ca5f1e5 with merge base 896178e ():

NEW FAILURES - The following jobs have failed:

• Apple / build-frameworks-ios / macos-job (gh)
  Failed to CreateArtifact: Unable to make request: ENOTFOUND
• pull / test-qnn-wheel-packages-linux (3.10) / linux-job (gh)
  RuntimeError: Command docker exec -t 6909d14e2e58eb45d29d96b9caf92bb0bc24dbd8625caa65c0270fd621c61f9e /exec failed with exit code 1
• pull / test-qnn-wheel-packages-linux (3.11) / linux-job (gh)
  RuntimeError: Command docker exec -t bdbe80c97d54263bda5159dbc608d73bf76651df9cebd3d2a56a1a4d13995425 /exec failed with exit code 1
• pull / test-qnn-wheel-packages-linux (3.12) / linux-job (gh)
  RuntimeError: Command docker exec -t 9ad0743f1a493808c75adf50a7f9a66e644690e729f46405bae2e76b22be6917 /exec failed with exit code 1
• pull / unittest-editable / windows / windows-job (gh)
  tools/cmake/common/preset_test.py::TestPreset::test_define_overridable_option_invalid_type

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