[naga spv-in] Support for OpAtomicCompareExchange

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Connections

Part of

• [spv-in] Atomics support #4489

PR

• feature: [spv-front] Support for OpAtomicCompareExchange, fixes #6296 #6590

Description

OpAtomicCompareExchange was removed from initial SPIR-V atomics support because it requires more infrastructure to support type-upgrading. Previous (now reverted) commits exist as a starting point to finish this work.

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Just a note to myself that while working on this, the command I use for testing is:

RUST_LOG=trace cargo watch -x 'test -p naga --features spv-in,wgsl-in,wgsl-out -- --nocapture atomic_compare_exchange'