[IRSim][IROutliner] Adding OptRemarks for the IROutliner.

[AndrewLitteken]

Summary

This places OptRemarks at each location where a decision is made to not outline, or to outline a specific section.

Test:

• llvm/test/Transforms/IROutliner/opt-remarks.ll

[AndrewLitteken]

Newline addition.

[jroelofs]

llvm/include/llvm/Transforms/IPO/IROutliner.h

282

Since this doesn't own the referred-to function, why not use an llvm::function_ref here like the others (GTTI, GIRSI)?

llvm/lib/Transforms/IPO/IROutliner.cpp

1560

FWIW, most diagnostics start with lowercase as their first letter.

1616

llvm::interleave might help here to avoid emitting the trailing space.

[AndrewLitteken]

Updating for function_refs, llvm::interleave and capitalization.

[jroelofs]

LGTM