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`.
If a `ctest_*` command has CAPTURE_CMAKE_ERROR then any errors generated
by cmake during that command will cause the value to be assigned `-1`.
This will prevent a `ctest -S` script from returning non-zero unless the
script explicitly calls `message(FATAL_ERROR)`.
