[CodeGen] Add support for multiple memory operands in MachineInstr::mayAlias
To support all targets, the mayAlias member function needs to support instructions with multiple operands.
This revision also changes the order of the emitted instructions in some test cases.
Reviewers: efriedma, hfinkel, craig.topper, dmgreen
Reviewed By: efriedma
Subscribers: MatzeB, dmgreen, hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D80161