Allows users to enable features if they are present, getting back a bool
telling them whether the feature is supported and will be enabled on the
device.
Also:
* Removes redundant VkPhysicalDeviceFeatures2 struct in vkb::PhysicalDevice.
* Adds test copying of details when creating a VkDevice so that test can check
what features were actually enabled on the device.
* Creates GenericFeatureChain struct for managing pNext chains.
* Allow multiple calls to set_require_features by combining the fields
Allows the tests to set the exact values vk-bootstrap will receieve
rather than require a real vulkan driver to be present on the system.
This is done by creating a `vulkan-1.dll` on windows that implements
all of the API functions, and on linux/macOS intercepts `dlsym` to
make it return the mock's functions.
