Multisite: Deprecate the blog_details filter.

`get_site()` has replaced `get_blog_details()` throughout core and is the recommended way to retrieve a current or single site object.

The `blog_details` filter is applied when full details are requested from `get_blog_details()`.

To ensure backwards compatibility in the switch to `get_site()`, this `blog_details` filter is now applied in `WP_Site::get_details()` and marked as deprecated with a note to rely instead on the `site_details` filter introduced in 4.6.

Props flixos90.
See #37102.
Fixes #38491.

Built from https://develop.svn.wordpress.org/trunk@38936


git-svn-id: http://core.svn.wordpress.org/trunk@38879 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-site.php

@@ -346,6 +346,9 @@ final class WP_Site {
 			}
 		}
 
+		/** This filter is documented in wp-includes/ms-blogs.php */
+		$details = apply_filters_deprecated( 'blog_details', array( $details ), '4.7.0', 'site_details' );
+
 		/**
 		 * Filters a site's extended properties.
 		 *