[llvm] Add __size_returning_new variant detection to TLI. (PR #101564)

[Snehasish Kumar via llvm-commits]

snehasish wrote:

Added a unittest to validate the return type (also updated up the return types in the test) in https://github.com/llvm/llvm-project/pull/102391. @nikic ptal, thanks!

https://github.com/llvm/llvm-project/pull/101564