Add Version newtype wrapper

[Rua]

Ash currently represents Vulkan API versions as u32, and has a bunch of bare functions and constants to deal with them. I think it would be more idiomatic if these were represented as a newtype wrapper Version. Then the constants can be associated constants, and the functions can be methods. I realise that Vulkan itself represents these as uint32_t, so recognising which values are versions may be more difficult.

[MarijnS95]

Curious how much this would conflict with #431 though, but it's definitely more idomatic to use a newtype and methods instead of free functions.

[Ralith]

Feel free to crib openxr::Version

[Rua]

Has there been any work on this?