[llvm] [BPF] Support Jump Table (PR #149715)

[Anton Protopopov via llvm-commits]

aspsk wrote:

Ok, my `bpf_goto_x` tests from RFC pass now with this branch (my kernel branch is [here](https://github.com/aspsk/bpf-next/tree/wip/indirect-jumps)). I will continue with adding support/tests for computed goto and addressing the comments from RFC (main ones left is on register liveness and removing min,max->index). [Just in case, I am on PTO in mountains this and the next week, and may be 100% offline on some days.]

https://github.com/llvm/llvm-project/pull/149715