new: [tools] Add PyMISP parity checker script

Python script that compares RustMISP's API surface and integration tests
against PyMISP to identify missing methods and test coverage gaps.

Run: python3 scripts/check_pymisp_parity.py [--pymisp-path /path/to/PyMISP]

Auto-detects PyMISP location, extracts methods via AST parsing and regex,
normalises name differences, and reports coverage with visual progress bars.

Current parity: 99.5% methods, 78.8% tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: iglocska