[clang] [SourceManager] Expose max usage of source location space as a Statistic (PR #96292)

[Utkarsh Saxena via cfe-commits]

usx95 wrote:

This is a simple enough patch, so I agree we can deal with concerns post-commit as well. Let's go ahead with landing this then.

https://github.com/llvm/llvm-project/pull/96292