Gfx: Explicit destroy_surface

[kvark]

Wold be good to have this explicit, matching Vulkan.

[yanchith]

I slowly started working on this, got the easiest part so far (hal, vulkan, and empty). Should finish on the weekend.

[yanchith]

Sorry this is taking a bit longer, but I've hit a few things where I
need a hint:

• Do we also want to add destroy_surface on trait Instance in hal,
  or just the various instance implementations in the backends
  (similar to create_surface)? I initally assumed the trait also,
  but am no longer so sure now that I discovered:

• Vulkan has vkDestroySurfaceKHR, I am pretty sure gl has nothing of
  the sort, but I am not familiar with metal, dx11 and
  dx12. After some searching, I wasn't able to find anything
  corresponding to destroy_surface in the other APIs. Should it be
  just a no-op in the case where API is not vulkan?

Thanks!

[kvark]

Let's have destroy_surface in trait Instance.

Having it as no-op is totally fine in some backends.
If you don't know what it has to do, leaving a //TODO is totally fine, since it's still not a regression from the current code.