Create a clang-tidy check to warn when -dealloc is implemented inside an ObjC class category.

Summary: Such implementations may override the class's own implementation, and even be a danger in case someone later comes and adds one to the class itself. Most times this has been encountered have been a mistake.

Reviewers: stephanemoore, benhamilton, dmaclach

Reviewed By: stephanemoore, benhamilton, dmaclach

Subscribers: dmaclach, mgorny, cfe-commits

Tags: #clang-tools-extra, #clang

Differential Revision: https://reviews.llvm.org/D72876