Add operator benchmark utility scripts

[baominghelly]

Summary

• add a CLI for generating deterministic operator benchmark inputs
• add a CLI for aggregating operator result JSON files
• document both workflows in scripts/README.md
• add focused tests for configuration generation, shape derivation, CLI validation, and aggregation

Why

The utility scripts are useful independently of the InfiniOps adapter implementation and made the adapter pull request unnecessarily large. Keeping them in a separate pull request gives the generator and reporting formats a focused review surface.

The generator also now emits linear weights as [K, N], matching the InfiniOps matrix contract and the generated [M, N] output.

Validation

• python3 -m pytest -q tests/test_operator_scripts.py: 6 passed
• Black 23.9.1 check: passed
• Flake8 7.3.0 check: passed
• Cambricon generator dry run for linear/mm/add: passed
• Aggregator CLI smoke test over 12 real MLU result files: passed

This PR is intentionally independent of the InfiniOps adapter in draft PR #47 and targets master directly.

Supersedes #46, which GitHub automatically closed when its head branch was renamed.