Multisite: Remove the output parameter from get_site()

Full `WP_Site` objects should be expected from `get_site()` rather than arrays.

In the single (soon to be deprecated) use of arrays for this in core, we can cast the result to `(array)` for back-compat.

See #35791.

Built from https://develop.svn.wordpress.org/trunk@37652


git-svn-id: http://core.svn.wordpress.org/trunk@37618 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/ms-functions.php

@@ -2488,7 +2488,7 @@ function wp_get_sites( $args = array() ) {
 	$results = array();
 
 	foreach ( $_sites as $_site ) {
-		$results[] = get_site( $_site, ARRAY_A );
+		$results[] = (array) get_site( $_site );
 	}
 
 	return $results;