[clang] [clang][Dependency Scanning] Report What a Module Exports during Scanning (PR #137421)

[Qiongsi Wu via cfe-commits]

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@@ -115,6 +115,15 @@ struct ModuleID {
   }
 };
 
+struct ExtendedModuleID {
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qiongsiwu wrote:

Oh I see what you meant. Thanks for the clarification. I agree using the STL as much as possible is a good idea. In our case here, I prefer the structure for the following reasons. 

1. There are a few use cases where we only use the `ID` field (e.g. [here](https://github.com/llvm/llvm-project/pull/137421/files#diff-6c14c5831345bba33e5cf69af62b76e8fea9d2d70474f6d9ccb024f99212c506R413)). It seems that `Info.first` is less readable than `Info.ID`.
2. I can add some documentation to the `struct`'s fields' names. I think I can do that with a pair as well, but it is less explicit. This is only a weak preference. 
3. It is easier to extend the `struct` if we need new fields. 

Does the above sound reasonable? If so I will keep what we have now. 

https://github.com/llvm/llvm-project/pull/137421