fix: move the dropdown div to a namespace instead of a class with only static properties (#5979)

* fix: remove drop down div class

* fix: change name and export for drop down div

* fix: make module-local variables conform to styleguide

* fix: format

* fix: shadowing

scripts/migration/renamings.js

@@ -1073,6 +1073,10 @@ const renamings = {
     'Blockly.blocks.variablesDynamic': {
       module: 'Blockly.libraryBlocks.variablesDynamic',
     },
+    'Blockly.DropDownDiv': {
+      module: 'Blockly.dropDownDiv',
+      path: 'Blockly.DropDownDiv',
+    },
   },
 };