[LifetimeSafety] Add loan expiry analysis (#148712)
This PR adds the `ExpiredLoansAnalysis` class to track which loans have expired. The analysis uses a dataflow lattice (`ExpiredLattice`) to maintain the set of expired loans at each program point.
This is a very light weight dataflow analysis and is expected to reach fixed point in ~2 iterations.
In principle, this does not need a dataflow analysis but is used for convenience in favour of lean code.
