DRA Derived Attributes

DRA currently relies on exact literal matching of device attributes across requests (matchAttributes). While performant, literal matching is rigid for end users. Workloads needing to pair devices across complex boundaries— such as extracting a PCI or NUMA ID from a topology string—cannot express these requirements inline. This KEP introduces derivedAttributes to .devices.requests. It allows users to synthesize virtual grouping keys on the fly using scoped, per-device CEL expressions. The scheduler's constraint engine then evaluates these derived keys exactly like static attributes.