Fix column_definition returning a wrong column:

- The issue was introduced in 9ad36e0.

  Now that a Column includes its cast type, the deduplicable feature
  that checks whether we have a colum in the cache would wrongly
  return an existing column that have the same type.
  https://github.com/rails/rails/blob/2ca006fb7fe881c225c000d9ab11e2a3554b70fa/activerecord/lib/active_record/connection_adapters/deduplicable.rb#L19
  https://github.com/rails/rails/blob/2ca006fb7fe881c225c000d9ab11e2a3554b70fa/activerecord/lib/active_record/connection_adapters/column.rb#L81

  And because the Type::DateTime doesn't override `==`,
  2 Type::DateTime objects would return true regardless of their
  timezone.

Author: Edouard-chin

activerecord/lib/active_record/type/internal/timezone.rb

@@ -16,6 +16,13 @@ def is_utc?
         def default_timezone
           @timezone || ActiveRecord.default_timezone
         end
+
+        def ==(other)
+          super(other) && timezone == other.timezone
+        end
+
+        protected
+          attr_reader :timezone
       end
     end
   end

activerecord/test/cases/base_test.rb

@@ -1982,4 +1982,12 @@ def test_protected_environments_are_stored_as_an_array_of_string
       assert_not ActiveRecord::Base.current_preventing_writes
     end
   end
+
+  private
+    def with_timezone_config(cfg, &block)
+      super(cfg) do
+        Default.reset_column_information
+        block.call
+      end
+    end
 end