Object management improvements

[CodingRays]

The object management upgrade is now basically feature complete.
The major changes are:

• Added surface and swapchain support
• Made a object set trait allowing custom object set implementations. This is already used for the swapchain.
• Remove object manager as it didnt really serve any purpose anymore. The allocator was moved as a publicly accessible feature to the DeviceContext.

There is still a lot of documentation work left and tests are missing for the swapchain object set since we cant expect a surface in a CI run. Not sure how to handle that issue.

[hYdos]

I'm a bit confused. You say that object manager has been removed but wasnt that the planned way to handle allocating objects?

[CodingRays]

The object manager used to handle that. But with the object set upgrade pretty much all of that code was moved into the specific object sets. The only thing left in the manager was the allocator. But realistically there is no reason why the allocator should be separate from the device so i moved it into the DeviceContext struct. Every device now has a publicly accessible allocator. As a result the object manager struct had no purpose anymore.