Updates to remove scale by default in favour of opt in via prop

As discussed here #16113 (comment), there is little point in having thumbnail preview and large popover preview showing the same thing.

Update to introduce a prop to opt in to scaling the preview. By default the preview is no auto-scaled.

Apply `true` value to `BlockPreview` to ensure that Block Styles popover preview is scaled to fit.

packages/block-editor/src/components/block-preview/index.js

@@ -18,7 +18,7 @@ import { useLayoutEffect, useState, useRef } from '@wordpress/element';
 import BlockEditorProvider from '../provider';
 import BlockList from '../block-list';
 
-export function BlockPreview( { blocks, settings, srcWidth = 400, srcHeight = 300 } ) {
+export function BlockPreview( { blocks, settings, srcWidth = 400, srcHeight = 300, scaleToFit = false } ) {
 	if ( ! blocks ) {
 		return null;
 	}
@@ -45,6 +45,9 @@ export function BlockPreview( { blocks, settings, srcWidth = 400, srcHeight = 30
 
 	// Dynamically calculate the scale factor
 	useLayoutEffect( () => {
+		if ( ! scaleToFit ) {
+			return;
+		}
 		// Retrieve the actual width of the element which wraps the preview
 		// note: this is not the preview itself, but the wrapper element
 		const destWidth = previewRef.current.offsetWidth;