[clang] [llvm] [clang][deps] Overload `Filesystem::exists` in `DependencyScanningFilesystem` to have it use cached `status` (PR #88152)

[Jan Svoboda via cfe-commits]

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jansvoboda11 wrote:

I assume clang-format was overly eager with this one, as these are just whitespace changes. Can we undo that?

https://github.com/llvm/llvm-project/pull/88152