native cfg alias is public but not documented

[kpreid]

Description
The current (22.0.0) documentation for Instance::enumerate_adapters() says:

pub fn enumerate_adapters(&self, backends: Backends) -> Vec<Adapter>

Available on native only.

“native” is insufficient information to help dependent crate authors write code that compiles under all conditions. The crate documentation does mention “Feature Aliases” but doesn't explain what “native” means. Dependents need to be able to exactly match this cfg condition (or at least a subset of it) to avoid compilation failures.

(But surely the dependent crate either needs enumerate_adapters or not, you ask? Well, in this case, it's just debug logging of available adapters, so if the information is unavailable, that's fine.)

I haven't looked to see if any of the other cfg aliases that are undocumented appear publicly.