[llvm-branch-commits] [Clang] Refactor allocation type inference logic (PR #163636)

[Marco Elver via llvm-branch-commits]

https://github.com/melver created https://github.com/llvm/llvm-project/pull/163636

This change refactors the logic for inferring allocated types out of `CodeGen`
and into a new reusable component in `clang/AST/InferAlloc.h`.

This is a preparatory step for implementing `__builtin_infer_alloc_token`. By
moving the type inference heuristics into a common place, it can be shared
between the existing allocation-call instrumentation and the new builtin's
implementation.