Atomics and Scalars are collapsed to the same LocalType

[atlv24]

Atomics and Scalars are collapsed to the same LocalType
https://github.com/gfx-rs/wgpu/blob/trunk/naga/src/back/spv/mod.rs#L360
Type capability requests are based on TypeInner
https://github.com/gfx-rs/wgpu/blob/trunk/naga/src/back/spv/writer.rs#L835
But deduplicated by LocalType
https://github.com/gfx-rs/wgpu/blob/trunk/naga/src/back/spv/writer.rs#L977

This means if an atomic<u64> is seen after u64, then the necessary Int64Atomics capability doesn't get requested.

LocalType should represent Atomic and non-Atomic types with distinct values, but I'm not sure how. Do we want a atomic: bool or an Atomic {} variant?

[atlv24]

Neither solution works, because type declarations must be unique. I'm going to lift the capability request call out of the lookup so it happens on every type instead

[teoxoy]

I'm going to lift the capability request call out of the lookup so it happens on every type instead

Sounds good, not sure why it was nested.