target/descriptor: Rework how parameter defaults are overridden.
target/descriptor: Rework how parameter defaults are overridden.

Instead of supplying only the parameter name and value to be set as a
default, allow for replacing the entire parameter object as this allow
more control over what needs overriding for a particular platform.

setrofim/workload-automation,setrofim/workload-automation,ARM-software/workload-automation,setrofim/workload-automation,ARM-software/workload-automation,setrofim/workload-automation,ARM-software/workload-automation,ARM-software/workload-automation