[llvm] [SandboxIR] Implement Instruction flags (PR #103343)

[Arthur Eubanks via llvm-commits]

https://github.com/aeubanks approved this pull request.

not a fan of the LLVM-side of this API (methods should really only be on FPMathOperator), but shrug

https://github.com/llvm/llvm-project/pull/103343