ume: Define VIAM definitions for the UME VADL specification #757
Description
The VIAM UserModeEmulation definition (and others) should model all aspects of the user mode emulation VADL specification in a well consumable (and potentially extensible) way.
In a first step, it is not required to add all UME feature configurations to the definitions, but only those, required to infer all values necessary to generate the UME implementation that was hardcoded in #756.