find_package is used to try to find the Vulkan-Headers, and if they aren't
present, it downloads them with fetch content. This way users don't need
vulkan 'installed' on their system, specifically for windows users.
It also changes the tests to load all the necessary function pointers, that
way we don't need to find the vulkan loader to build the tests.
Added device::get_queue_families() to facilitate custom queue setups
get_swapchain_images() renamed to get_image(), made member function to
swapchain.
get_swapchain_image_views() renamed to get_image_views(), also moved to
member function of swapchain
fixed bug with headless instance not being correct
Stopped Catch2 from polluting the buildable targets
