[clang] [clang-tools-extra] [clang-tidy] EndSourceFile() for preprocessor before diagnostic client (PR #145784)

[Jan Korous via cfe-commits]

https://github.com/jkorous-apple approved this pull request.

I want to check that my mental model of InSourceFile is correct but otherwise LGTM.

https://github.com/llvm/llvm-project/pull/145784