Right now the logic checking if CPU features used before checkpoint match current CPU features is in VM code. VM stores and retrieves CPU features through C/R API's user_data extension. This is convenient when we have a single image that can be either accepted or rejected, but does not offer the flexibility for C/R engine to select the best image for current execution environment.

The goal of this issue is to move to a declarative API that will express the requirements using more abstract means, labels (for CPU architecture) and bitmaps (for CPU features).