StoreGate: WDHK dependency fix.

WriteDecorHandleKey is meant to be compatible with a WriteHandleKey for the same container. It had code to suppress a circular dependency error if the two keys were used by the same component, but we could still get a warning if two such keys were used by different components under the same algorithm.

Extend this to work across all components of an algorithm, but try to only suppress the warning if the component with the WriteHandleKey is encountered before the component with the WriteDecorHandleKey.

Test it in AthExStoreGateExample and ControlTest.