[clang-tidy]: Google: new check 'google-upgrade-googletest-case'

Introduce a new check to upgrade user code based on API changes in Googletest.

The check finds uses of old Googletest APIs with "case" in their name and replaces them with the new APIs named with "suite".

Patch by Alex Strelnikov (strel@google.com)
Reviewed as D62977.

llvm-svn: 367263