Support multiple versions of `raw-window-handle` concurrently?

[MarijnS95]

Supporting multiple version would be nice of course but currently I can't estimate the overhead for this as I haven't been following the rwh api changes lately tbh

Supporting multiple versions on the producer end is really easy via just implementing the traits for each version of the crate (feature-gated so that you don't have to have duplicate raw-window-handle dependencies). However, doing this for the consumer end (here and in ash-window for example) is more problematic as we should essentially have multiple versioned functions of metal_layer_from_handle() for each version of raw-window-handle, Alternatively we could implement a conversion trait for every version of raw-window-handle.

@notgull suggestions (preferably in a separate issue/PR/discussion)?

Originally posted by @MarijnS95 in #10 (comment)

[notgull]

From this crate's API, it looks like "multiple versioned functions of metal_layer_from_handle() for each version of raw-window-handle" is probably the only good option.

[MarijnS95]

So we'd end up with metal_layer_from_raw_window_handle_05() etc. Probably the same for ash-window even though unfortunately that match block is much bigger?