[llvm] [DTLTO][Windows] Expand short 8.3 form paths in ThinLTO module IDs (PR #178303)

[Teresa Johnson via llvm-commits]

teresajohnson wrote:

> @teresajohnson I have pushed a change to address your suggestions. However, while adding those comments, I realized that several existing comments and function names in this class were still archive-specific, even though the class’s responsibilities have expanded to support FatLTO objects and path normalization. I have updated them to better reflect the class’s broader role. The member functions `saveInputArchiveMember` and `saveInputArchiveMembers` were removed entirely by inlining their logic. Finally, since I found it difficult to recall some details of the class’s operation, I added a class-level comment describing its overall responsibility and behavior.
> 
> However, I remember that in a previous PR you asked me to pull out as many of the NFC refactors as I could. If you think these refactors are acceptable, I could do the same here.

Yeah that all looks good but please go ahead and commit it separately in an NFC patch (lgtm on that)

https://github.com/llvm/llvm-project/pull/178303