This makes getAliasingOpResult symmetric to getAliasingOpOperand. The previous implementation was confusing for users and implemented in such a way only because there are currently no bufferizable ops that have multiple aliasing OpResults.
Differential Revision: https://reviews.llvm.org/D119259
They used to be classes with a virtual `run` function. This was inconvenient because post analysis steps are stored in BufferizationOptions. Because of this design choice, BufferizationOptions were not copyable.
Differential Revision: https://reviews.llvm.org/D119258