This commit also strips the old copyright comment header in touched
files, as those will also be replaced with a more standardized and
machine-friendly version.
These files are not included by the default
`#include <catch2/catch_test_macros.hpp>` path, so that users do
not have to pay for them if they do not use them. Follow up is to
split out the small part of `catch_preprocessor.hpp` used by the
default test macros (AFAIK, it is just `INTERNAL_CATCH_REMOVE_PARENS`
macro), so that it is not included by the default path either.
Also fixes#1892 by providing the missing macros.
