[llvm] [RFC][BPF] Support Jump Table (PR #133856)

[via llvm-commits]

yonghong-song wrote:

Just uploaded a version on top of latest llvm-project and merged with additional changes from @eddyz87. Note that there is a test failure
```
LLVM :: Transforms/InferAddressSpaces/SPIRV/generic-cast-explicit.ll
```
which also failed with latest llvm-project.

I will update later once this test failure is gone from upstream.

https://github.com/llvm/llvm-project/pull/133856