Allows build options specific to Vulkan-Utility-Libraries to be
easily grouped via cmake-gui.
This approach is also nicer for users who consume the library via
add_subdirectory or FetchContent since it more obvious what
settings are being ovverriden.
Remove UTILITY_LIBRARIES_CPP_STANDARD since we don't have a
reason to support multiple CPP standards.
Set testing to OFF by default to make consuming the library easier
for users and package managers.