Handle trailing slashes in rest_preload_api_request

[spacedmonkey]

When passing a path to rest_preload_api_request that ends in query string, ensure that the parsed path also is untrailingslashit. Follow up to #51636

[antonvlasenko]

I'm working on a patch for this issue.

Trac ticket: https://core.trac.wordpress.org/ticket/57048

[antonvlasenko]

The ​proposed PR updates the rest_preload_api_request function to remove trailing slashes from path parth of the request when preloading data for a specified REST API path.

Before patch:
Preloading /wp/v2/types//?media// would return an array with preloaded data keyed as /wp/v2/types//?media. Only slashes at the end of the path were removed.

After patch:
The path would be /wp/v2/types?media.

Steps to test this PR:

1. Login to the admin panel.
2. Edit an existing post or create a new one and then click Edit.
3. Open the dev tools, inspect the source code of the page. You should see a call to the wp.apiFetch.createPreloadingMiddleware() function and the preloaded data passed as an argument of that function. Typical preloaded requests are:
   • /wp/v2/types?context=view
   • /wp/v2/taxonomies?context=view
   • /wp/v2/blocks?context=edit&per_page=-1
   • /wp/v2/posts/<post-ID>?context=edit
   • /wp/v2/types/post?context=edit
   • /wp/v2/settings