[llvm] [SandboxIR] Implement StoreInst (PR #99707)

[Alina Sbirlea via llvm-commits]

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

LGTM.

On the first suggestion comment: deviating from the class hierarchy should be transparent to the user of the APIs. It would reduce some of the duplication, so it is worth considering to do in a follow-up NFC (i.e. both are).

https://github.com/llvm/llvm-project/pull/99707