test: Introduce special cases for affected test files
test: Introduce special cases for affected test files

Firstly never consider `test/verify/check-example` to be affected.
We will use it for testing of retry logic for failed tests which does
not work if test is changed. That would mean we could never update this
file.
We are not losing anything by doing this special case but it makes it
much simpler to introduce tests for the retry logic.

Secondly never ignore changes in `test/verify/check-testlib`.
It might happen that some PR will change more than 3 test files. In this
case we would not consider this file to be affected thus breaking test,
which needs it to be considered as affected.

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