[llvm] [SandboxVec] Add pass to create Regions from metadata. Generalize SandboxVec pass pipelines. (PR #112288)

[Arthur Eubanks via llvm-commits]

https://github.com/aeubanks commented:

lgtm at a high level

would be good to get a test in with multiple function passes, perhaps with a `null` function pass

https://github.com/llvm/llvm-project/pull/112288