Update mappings to use $resolveReference operation

[paynejd]

Note that mappings generally do not specify a repo version and it should not resolve to a repo version unless it is explicit in the definition. Currently, $resolveReference always resolves to a specific repo version, so we may need to add a flag to optionally resolve just to a version-less repo. Let's discuss.

[snyaggarwal]

@paynejd This is duplicate of #1747. Please close this if you agree