MONGOID-5414 deprecate criteria cache functionality (#5383)

* MONGOID-5414 remove references to contextual/criteria cache

* MONGOID-5414 fix criteria tests

* MONGOID-5414 add deprecation tags

* MONGOID-5414 remove deprecated methods

* MONGOID-5414 add release note

* MONGOID-5414 fix tests

Author: neilshweky

source/release-notes/mongoid-8.0.txt

@@ -719,3 +719,12 @@ Support Dropped for the ``:id_sort`` Option on ``#first/last``
 
 Support for the ``:id_sort`` option on the ``#first`` and ``#last`` options has
 been dropped. These methods now only except a limit as a positional argument.
+
+
+Support Dropped for Mongoid::Criteria cache
+-------------------------------------------
+
+Support for individually caching criteria objects has been dropped in Mongoid 8.
+
+In order to get caching functionality, enable the Mongoid QueryCache. See the
+section on :ref:`QueryCache <query-cache>` for more details.