[clang-tidy] performance-unnecessary-copy-initialization: Check for const...

[clang-tidy] performance-unnecessary-copy-initialization: Check for const reference arguments that are replaced template parameter type.

This fixes false positive cases where a non-const reference is passed to a
std::function but interpreted as a const reference.

Fix the definition of the fake std::function added in the test to match
std::function and make the bug reproducible.

Reviewed-by: aaron.ballman

Differential Revision: https://reviews.llvm.org/D90042