feat(heuristics): add Fake Email analyzer to validate maintainer email domain

[AmineRaouane]

Summary

This PR adds a new heuristic analyzer called FakeEmailAnalyzer. It verifies the validity of maintainer email addresses listed in a PyPI package by checking both the format and the existence of MX records for their domains. This helps detect packages with fake or throwaway emails, which are often indicative of malicious intent.

Description of changes

• Implemented FakeEmailAnalyzer that:
  • Validates email format using a regex.
  • Verifies the existence of MX records for the email domain via DNS resolution.
• Updated detect_malicious_metadata_check.py to include and invoke this new analyzer.
• The analyzer handles DNS errors and skips analysis if no email is present.
• The logical reason for combining quickUndetailed with a failed(Heuristics.FAKE_EMAIL.value) is that a package that is rushed onto a platform by someone using a fake email address points to an actor who may be trying to quickly distribute a package while obscuring their identity and avoiding being investigated.

Related issues

None

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