[clang] [LifetimeSafety] Add missing origins stats for lifetime analysis (PR #166568)

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DEBADRIBASAK wrote:

> I expect all the types to still be available when we print these stats. These are stored in the ASTContext and that one is destroyed very late.

If we use `Type*` as the key, constructing the string is not feasible as it is done by `TypePrinter` object which is part of anonymous namespace in `TypePrinter` file. Also, if we want to just store the pointer to the `QualType` returned by `getType` function of expression pointer it will store the dangling reference to a temporary object.

https://github.com/llvm/llvm-project/pull/166568