Description

Preloading middleware doesn't return consistent responses for OPTIONS type requests if the parse option is set to false.

This PR aims to fix the preloading middleware so that it returns window.Response object if the parse option is set to false.
Although this is a breaking change I haven't noticed any issues with preloading.

Fixes #37966

How has this been tested?

1. Go to the Gutenberg -> Experiments page and enable the Navigation screen feature.
2. Save the changes.
3. Open the Gutenberg -> Navigation page.
4. Open the console, run the following code:

wp.apiFetch.use(wp.apiFetch.createPreloadingMiddleware(
	{
		"OPTIONS": {
			"/someUrl": {
				'body': 'From middleware',
				'headers': {}
			}
		}
	}));

5. Run the following code in the console:

wp.apiFetch( {
	path: "/someUrl",
	method: 'OPTIONS',
        parse: false
} ).then( res  => {
	console.log( res );
} );

Expected result (after the fix):

You should see Response object in the console (please see the screenshot), because we chose not to parse the response (parse: false).

Actual result (before this fix):

You will see From middleware text in the console as if the response was parsed.

Screenshots

Types of changes

Bug fix

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).
• I've updated related schemas if appropriate.