[clang] [Driver] Add an option to disable default config filenames

Add a `--no-default-config` option that disables the search for default
set of config filenames (based on the compiler executable name).

Suggested in https://discourse.llvm.org/t/rfc-adding-a-default-file-location-to-config-file-support/63606.

Differential Revision: https://reviews.llvm.org/D134018