Add cmake variable CMAKE_TEST_LAUNCHER and property TEST_LAUNCHER

The book "Professional CMake" mentions that the cmake target property CROSSCOMPILING_EMULATOR can be used as a launcher #23672 (comment 1210867), but this has limitations and can only be used for cross-compiling in the future as mentioned at #23672 (closed).

This merge request provides a new and independent option. Executable cmake targets are hereby given a new property TEST_LAUNCHER, which can be used to specify a launcher that is also provided via the file api for integration into IDEs.

Issue: #23672 (closed)
Requires: !8964 (merged)