[clang-tools-extra] [clang-tidy] performance-unnecessary-copy-init: Add a hook... (PR #73921)

[Piotr Zegar via cfe-commits]

PiotrZSL wrote:

In theory changes that are required for "private" checks should be done by you on some own private fork instead of adding that "unused" code here. But only option I see is simply moving diagnostic to separate methods, and make those methods virtual. That could be +- acceptable. Or moving "condition" into separate method. Adding empty methods & ifs to call that method is not an option. 

https://github.com/llvm/llvm-project/pull/73921