Privacy: Rename `wp_get_user_request_data()` to `wp_get_user_request()` for...

Privacy: Rename `wp_get_user_request_data()` to `wp_get_user_request()` for clarity; deprecate the old function.

The function returns an instance of the `WP_User_Request` object itself, not its `$request_data` property.

Follow-up to [44606].

Props garrett-eclipse.
Fixes #46302.
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git-svn-id: https://core.svn.wordpress.org/trunk@47045 1a063a9b-81f0-0310-95a4-ce76da25c4cd