Use config variable for admin set in more places.

For collection and admin set

Admin Sets were appearing twice, once via their gid, and once via their
model. This change moves them to work like other collections.

The admin set create service cannot create an AdminSet. Changing to use
the config variable causes specs to break, because they are using the
default config value of AdminSet.

This is the first step to locking down the change. The default fallback
value to AdminSet should probably be changed as well.

The config admin set class should not fall back to AdminSet, since
the default admin set service cannot create an AdminSet.

Links for Admin sets in collection type dropdown have changed.

calling wrong method

Shared specs are still failing.

Base class on config for admin_set_model rather than the use_valkyrie flag

* double_combo:
  ☑️ Add stubbing
  🐛 Favor helper method over instance variable
  Extracting a collection models method
  💄 endless and ever appeasing of the coppers
  ♻️ Stub incidental query
  ♻️ Consider all of the curation concerns

Throughout the code we have quite a bit of conditionals regarding what
is a work, collection, file_set, and adminsitrative set.  This model
attempts to provide a common point to interrogate the application.

There are, at present, no refactors to use this model.

Consider how our specs and our application are inconsistent in their
declaration/configuration/stubbing.  This model should help with that.

Instead of the myriad of ways of asking about which models to use, let's
leverage a consolidated central place for information.

This is but one step in addressing other issues.

…n-set-resources

* extract-hyrax-model-registry:
  🐛 Favor helper method over instance variable
  Favor helper method over instance variable
  ♻️ Favor dynamic value
  ♻️ Favor helper method
  ☑️ Fix stubbing
  Adding case statement
  ♻️ Fixing spec
  ♻️ Favor Hyrax::ModelRegistry
  💄 endless and ever appeasing of the coppers
  ♻️ Leverage Hyrax::ModelRegistry for ability tests
  ♻️ Favor Hyrax::ModelRegistry for search builders
  ♻️ Extracting naming container
  🧹 Expose Hyrax.config.use_valkyrie=