For policy-specific tests, use the version before the policy was
introduced. Otherwise, use 3.5 where possible.
Also, remove `cmake_minimum_required()` and `project()` calls from
individual cases where they are handled by `CMakeLists.txt`.
Support of 'new build system' in Xcode fixes indirectly few issues
which were caused by workaround with `XCODE_DEPEND_HELPER.cmake`
autogenerated script.
This patch adds test which is originated from issue #20260 and
reproduces this issue when 'new build system' is disabled.
Fixes: #20260