Add VulkanLibrary as first initialization step before Instance

[Rua]

Changelog:

- **Breaking** Changes to `Instance` and Vulkan initialization:
  - `FunctionPointers` is renamed to `VulkanLibrary`, and now resides in a separate `library` module. It is re-exported from the crate root.
  - The `Loader` trait is now in the `library` module.
  - `Instance` now requires a `VulkanLibrary` object, which you must create beforehand.
  - The `auto_loader` function is removed.
  - Supported extensions and layers are now retrieved from the `VulkanLibrary` object. The old `layers_list` and `InstanceExtensions` methods are removed.
  - The deprecated methods of `DeviceExtensions` are removed.
  - Vulkano-win: `required_extensions` now requires a reference to `VulkanLibrary`.
- **Breaking** Changes to Vulkano-util:
  - Required instance extensions for surface creation aren't added until `VulkanoContext` is created.
  - The `instance`, `device`, `graphics_queue` and `compute_queue` methods of `VulkanoContext` now return a reference instead of an owned `Arc`.

This closes #1876 by partially reimplementing it, but differently.

This is still a draft, because I ran into a problem making Vulkano-util conform to the new API. VulkanoConfig has a Default implementation, but that no longer works now that the user must load the library themselves. @hakolao do you know of a good solution to this? If you think it's better, I can leave this PR as is, and give you the opportunity to fix it yourself later.

[hakolao]

I’ll try to come up with something later today, cant think of a good solution right away.

[hakolao]

@Rua How about something like this?

So the required extensions can be appended to the inputs from config. That way Default can remain None, and user can still add the extensions that they want, which are not required extensions.

On top of that, I think that the VulkanLibrary should probably be accessible from VulkanoContext? Unless it can be retrieved through instance. Either would be fine I think.

[Rua]

This is now ready for review.

[AustinJ235]

Looks good!