[llvm-branch-commits] [Clang][CodeGen] Emit !alloc_token for new expressions (PR #162099)

[Marco Elver via llvm-branch-commits]

https://github.com/melver created https://github.com/llvm/llvm-project/pull/162099

For new expressions, the allocated type is syntactically known and we
can trivially emit the !alloc_token metadata. A subsequent change will
wire up the AllocToken pass and introduce appropriate tests.