[IROutliner] Adding support for swift errors

[AndrewLitteken]

Summary

Since some values can be swift errors, we need to make sure that we correctly propagate the parameter attributes.

Tests found at:
llvm/test/Transforms/IROutliner/outlining-swift-error.ll

[jroelofs]

llvm/lib/Transforms/IPO/IROutliner.cpp

795–797

With Optionals, we usually avoid calling hasValue()/getValue() most of the time, and instead treat them as if they had pointer semantics. Subjectively, this increases readability.