IR: Fix use-list-order round-tripping for call and invoke

Fix the use-list-order for call and invoke instructions by setting the
operands in order of their index. This matches the use-list-order
prediction. Note that the verifier precludes sharing operands in callbr
(so there was no bug to fix), but that code was updated for consistency.

Bug was found during review of https://reviews.llvm.org/D104740.

Differential Revision: https://reviews.llvm.org/D104805