* filter out duplicates in GetOpenDeclarations

* Add rec module to unused opens test

* add unused opens tests for rec modules

* fix unused opens for rec modules

* filter out symbol uses that lays above the open statement

* filter out union cases definitions

* fix ItemsAreEffectivelyEqualHash for Item.ModuleOrNamespaces

* use Dictionary to lookup symbol uses by declaring entity

* formatting

* cleanup

* use Dictionary to filter out already processed modules

* add BagAdd and BagExistsValueForKey Dictionary extensions