[llvm] [SandboxIR] Add more Instruction member functions (PR #98588)

[Arthur Eubanks via llvm-commits]

aeubanks wrote:

> rst is the default. There is no markdown. https://github.com/llvm/llvm-project/blob/main/llvm/docs/SphinxQuickstartTemplate.rst

there are multiple `.md` files in `llvm/docs` that are rendered, e.g. https://llvm.org/docs/AssignmentTracking.html comes from `llvm/docs/AssignmentTracking.md`


https://github.com/llvm/llvm-project/pull/98588