fix: cleanup PyPI package temp directory and prevent leaks

[behnazh-w]

Summary

Fix PyPI package temp directory cleanup leaks during malware/source analysis.

Description of changes

• Strip the single top-level sdist archive directory during extraction, so package contents are extracted directly into the mkdtemp root.
• Ensure source and wheel context managers clean up temp directories even when analysis raises.
• Use the sourcecode context manager in TypeStubFileAnalyzer instead of calling download_sourcecode() directly.
• Add relevant unit tests for cleanup after extraction.