[clang Dependency Scanning] Enhance File Caching Diagnostics (#144105)

`DependencyScanningFileSystemSharedCache` can currently report
out-of-date negatively stat cached paths. This PR enhances the reporting
with two modifications.

1. The reported path are now null terminated char arrays instead of
`StringRef`s. This way the API's user can avoid copying `StringRef`s to
other containers because the char arrays can be used directly.
2. The API now reports out-of-date cache entry due to file size changes.
Specifically, we check each file's cached size against the size of the
same file on the underlying FS. If the sizes are different, diagnostics
will be reported.

rdar://152247357

0 files changed, 0 insertions, 0 deletions