Allow swapchain binding to compute shaders

[kvark]

Is your feature request related to a problem? Please describe.
For compute-only workloads, such as piet-gpu it's ideal to just write to the swapchain directly. However, this isn't portable.

Describe the solution you'd like
A native-only feature that exposes this capability.

Describe alternatives you've considered
Forcing a copy for all of these users.

Additional context

[cwfitzgerald]

This is now allowed, but you can't query the supported usages from the swapchain.

[cwfitzgerald]

This is now queryable