Fix collections names no longer unique when moved around

We were not checking for uniqueness after moving. And in some cases the new
siblings of our collection may have conflicting names.

tests/python/view_layer/CMakeLists.txt

@@ -62,7 +62,8 @@ endmacro()
 
 VIEW_LAYER_TEST(active_collection)
 VIEW_LAYER_TEST(background_set)
-VIEW_LAYER_TEST(collection_rename)
+VIEW_LAYER_TEST(collection_rename_a)
+VIEW_LAYER_TEST(collection_rename_b)
 VIEW_LAYER_TEST(evaluation_render_settings_a)
 VIEW_LAYER_TEST(evaluation_render_settings_b)
 VIEW_LAYER_TEST(evaluation_render_settings_c)

tests/python/view_layer/test_collection_rename_b.py

@@ -0,0 +1,58 @@
+# ############################################################
+# Importing - Same For All Render Layer Tests
+# ############################################################
+
+import unittest
+import os
+import sys
+
+from view_layer_common import *
+
+
+# ############################################################
+# Testing
+# ############################################################
+
+class UnitTesting(ViewLayerTesting):
+    def setup_collections(self):
+        import bpy
+        scene = bpy.context.scene
+
+        master = scene.master_collection
+        one = master.collections[0]
+        two = master.collections.new()
+        sub = two.collections.new(one.name)
+
+        self.assertEqual(one.name, sub.name)
+
+        lookup = {
+            'master': master,
+            'one': one,
+            'two': two,
+            'sub': sub,
+        }
+        return lookup
+
+    def test_move_above(self):
+        collections = self.setup_collections()
+        collections['sub'].move_above(collections['one'])
+        self.assertNotEqual(collections['one'].name, collections['sub'].name)
+
+    def test_move_below(self):
+        collections = self.setup_collections()
+        collections['sub'].move_below(collections['one'])
+        self.assertNotEqual(collections['one'].name, collections['sub'].name)
+
+    def test_move_into(self):
+        collections = self.setup_collections()
+        collections['sub'].move_into(collections['master'])
+        self.assertNotEqual(collections['one'].name, collections['sub'].name)
+
+
+# ############################################################
+# Main - Same For All Render Layer Tests
+# ############################################################
+
+if __name__ == '__main__':
+    UnitTesting._extra_arguments = setup_extra_arguments(__file__)
+    unittest.main()