224873d7ac
In preparation of adding the "AllocToken" pass, add the pre-requisite `sanitize_alloc_token` function attribute and `alloc_token` metadata. --- This change is part of the following series: 1. https://github.com/llvm/llvm-project/pull/160131 2. https://github.com/llvm/llvm-project/pull/156838 3. https://github.com/llvm/llvm-project/pull/162098 4. https://github.com/llvm/llvm-project/pull/162099 5. https://github.com/llvm/llvm-project/pull/156839 6. https://github.com/llvm/llvm-project/pull/156840 7. https://github.com/llvm/llvm-project/pull/156841 8. https://github.com/llvm/llvm-project/pull/156842