[clang-tidy] Do not trigger unnecessary-value-param check on methods marked as final

Summary: Virtual method overrides of dependent types cannot be recognized unless
they are marked as override or final.

Exclude methods marked as final from check and add test.

Reviewers: sbenza, hokein, alexfh

Subscribers: malcolm.parsons, JDevlieghere, cfe-commits

Differential Revision: https://reviews.llvm.org/D27248

llvm-svn: 288502