[llvm] [NFC][DebugInfo] Wrap DILineInfo return type with std::optional to handle missing debug info. (PR #129792)

[David Blaikie via llvm-commits]

https://github.com/dwblaikie approved this pull request.

Still seems like this might benefit from being split up a bit more (looks like there are some more places in this patch that have changes in behavior that aren't tested, like MachODump.cpp, maybe), but I guess it'll do.

https://github.com/llvm/llvm-project/pull/129792