[llvm] [SandboxIR] Adds BasicBlock and adds functionality to Function and Context (PR #97637)

[Arthur Eubanks via llvm-commits]

https://github.com/aeubanks commented:

nit: git commit titles are usually imperative, e.g. `Add ...` instead of `Adds ...`

https://github.com/llvm/llvm-project/pull/97637