Constrain processing of repo versions to be "consistent" within an expansion

[paynejd]

Resolved repo version must be reused while evaluating the expansion to avoid the risk of an equivalent repo reference being evaluated differently while processing. For example, if I have several concept references to CIEL and a new version of CIEL is released while the expansions is being generated, then some of those concepts will point to an old version of CIEL and some to the new version of CIEL - we want to ensure that all of them point to the same repo version that was originally resolved

Processing method:

• For each reference...
  • Check if reference has already been resolved to a repo version
    • If yes, use the "cached" repo version
    • If no, resolve the reference to a repo version
  • Evaluate the reference using the above repo version

NOTE: One ref can result in multiple repo versions (e.g. can include a system and one or more valuesets)