Improve support for DescribedValue in PropertyDescriptor.Builder

Since allowableValues() supports DescriptedValue it makes sense to use them in the dependsOn() and defaultValue() methods so it wouldn't be required to explicitly get the value of a DescribedValue when it is already used in allowableValues.

Raised here: https://github.com/apache/nifi/pull/6619#discussion_r1014953245