[clang-tools-extra] [clang-tidy] Add IgnoreAboveThreshold option to readability-function-cognitive-complexity (PR #178965)

[Carlos Galvez via cfe-commits]

carlosgalvezp wrote:

I would prefer something like `FunctionsToIgnore` instead of a silent threshold that hides the debt, like I wrote in the issue. But I won't die on this hill :) 

https://github.com/llvm/llvm-project/pull/178965