[Security] Added edge cases for tainted pickle deserialization

[theinfosecguy]

• Added pattern-not conditions to exclude safe usage patterns and minimize false positives.
• Added new test cases to cover a wider range of scenarios, including both vulnerable and safe usage patterns.

The patterns like pickle.load(pickle.dumps(...)) are added to pattern-not to avoid false positives in situations where the data being deserialized is explicitly serialized using pickle.dumps() within the same codebase.