Use a per-resolver ivydata file for caching dynamic mrids.

This allows resolvers to cache what latest.integration/etc. mean to them
regardless of whether their value is the latest value across all resolvers.

(Previously latest.integration could only be cached once per mrid, so
whichever resolvers were not latest would end up having to hit the network
each time retrieve was ran.)
Merge branch '1430_cache_dynamic_mrids_per_resolver' into bizo

* 1430_cache_dynamic_mrids_per_resolver:
  Use a per-resolver ivydata file for caching dynamic mrids.