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

[via llvm-commits]

yonghong-song wrote:

@aspsk @eddyz87 Just update the patch with following:
  - Change minimum jump-table-entries (for switch statements) to be 13, so if you intends to test with less switch statements, you can add option '-mllvm -bpf-min-jump-table-entries=<n>' (e.g., n = 3).
  - I added three tests to cover switch statement, blockaddress and globalvar.

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