[llvm] [BPF] expand mem intrinsics (memcpy, memmove, memset) (PR #97648)

[Yingchi Long via llvm-commits]

inclyc wrote:

Hi @yonghong-song ,

Do you think it is a nice option to add some mem intrinsics into the kernel? Thus we can combine & generate such intrinsics, and verifier can easily recognize it (if it is just a `BPF_CALL`).

https://github.com/llvm/llvm-project/pull/97648