[clang] [clang][scan-deps] Report a scanned TU's visible modules (PR #147969)

[Cyndy Ishida via cfe-commits]

cyndyishida wrote:

> In my local performance testing, there was no observable performance impact.

To expand on what I tested, `clang-scan-dep` wall time for: 
* scanning a TU that includes every clang module under `/S/L/F` in the macOS 26 sdk. 
* scanning a real Objective-C-based project, that already took ~60 seconds to scan on my 10-core machine without my changes. 

All of these cases were tested 10 times with a clean &  prepopulated module cache. 

https://github.com/llvm/llvm-project/pull/147969