[LifetimeSafety] Implement a basic use-after-free diagnostic

[usx95]

Implement use-after-free detection in the lifetime safety analysis with two warning levels.

• Added a LifetimeSafetyReporter interface for reporting lifetime safety issues
• Created two warning levels:
  • Definite errors (reported with -Wexperimental-lifetime-safety-permissive)
  • Potential errors (reported with -Wexperimental-lifetime-safety-strict)
• Implemented a LifetimeChecker class that analyzes loan propagation and expired loans to detect use-after-free issues.
• Added tracking of use sites through a new UseFact class.
• Enhanced the ExpireFact to track the expressions where objects are destroyed.
• Added test cases for both definite and potential use-after-free scenarios.

The implementation now tracks pointer uses and can determine when a pointer is dereferenced after its loan has been expired, with appropriate diagnostics.

The two warning levels provide flexibility - definite errors for high-confidence issues and potential errors for cases that depend on control flow.

[usx95]

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• [LifetimeSafety] Implement a basic use-after-free diagnostic #149731 👈 (View in Graphite)
• [LifetimeSafety] Add loan expiry analysis #148712 : 1 other dependent PR (#148976 )
• [LifetimeSafety] Revamp test suite using unittests #149158
• [LifetimeSafety] Add per-program-point lattice tracking #149199
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