Columns: Avoid re-render and subsequent action dispatch by adopting m…

…odule constant (#7720)

We were passing a new allowedBlocks reference on each column render. This dispatch additional unnecessary further actions to update inner block settings.
allowedBlocks reference should only be changed if, in fact, we are changing the allowedBlocks.
In the columns block, we can make allowed block a constant given that it never changes.

This problem may cause noticeable lag when writing/using columns because updating the InnerBlock setting may cause another rerender and another rerender updates the settings again. So this change prevents cascade re-renders.

core-blocks/columns/index.js

@@ -23,6 +23,8 @@ import {
 import './style.scss';
 import './editor.scss';
 
+const ALLOWED_BLOCKS = [ 'core/column' ];
+
 /**
  * Returns the layouts configuration for a given number of columns.
  *
@@ -145,7 +147,7 @@ export const settings = {
 					<InnerBlocks
 						template={ getColumnsTemplate( columns ) }
 						templateLock="all"
-						allowedBlocks={ [ 'core/column' ] } />
+						allowedBlocks={ ALLOWED_BLOCKS } />
 				</div>
 			</Fragment>
 		);