[clang-tidy] Adding a new modernize use nodiscard checker

Summary: Adds a checker to clang-tidy to warn when a non void const member function, taking only parameters passed by value or const reference could be marked as '[[nodiscard]]'

Patch by MyDeveloperDay.

Reviewers: alexfh, stephenkelly, curdeius, aaron.ballman, hokein, JonasToth

Reviewed By: curdeius, JonasToth

Subscribers: Eugene.Zelenko, lefticus, lebedev.ri, mgorny, xazax.hun, cfe-commits

Tags: #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D55433

llvm-svn: 350760