[clang] [LifetimeSafety] Implement a basic use-after-free diagnostic (PR #149731)

[Yitzhak Mandelbaum via cfe-commits]

================
@@ -66,6 +88,7 @@ using OriginID = ID<struct OriginTag>;
 // TODO(opt): Consider using a bitset to represent the set of loans.
 using LoanSet = llvm::ImmutableSet<LoanID>;
 using OriginSet = llvm::ImmutableSet<OriginID>;
+using ExpiredLoanMap = llvm::ImmutableMap<LoanID, const Fact *>;
----------------
ymand wrote:

Maybe comment? including -- what kind of facts do we expect as values?

https://github.com/llvm/llvm-project/pull/149731