[CodeExtractor] Making the arguments outlined easier to access from the outside

The Code Extractor does not provide an easy mechanism for determining the
inputs and outputs after extraction has occurred, this patch gives the
ability to pass in empty SetVectors to be filled with the inputs and
outputs if they need to be analyzed.

Added Tests:
- InputOutputMonitoring in unittests/Transforms/Utils/CodeExtractorTests.cpp

Reviewers: paquette

Differential Revision: https://reviews.llvm.org/D106991