[clang-tidy] Add a diagnostic callback to parseConfiguration

Currently errors detected when parsing the YAML for .clang-tidy files are always printed to errs.
For clang-tidy binary workflows this usually isn't an issue, but using clang-tidy as a library for integrations may want to handle displaying those errors in their own specific way.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D92920