blogger.getUsersBlogs doesn't work on Multisite when HTTPS is enforced

[dd32]

The XML-RPC endpoint blogger.getUsersBlogs doesn't work on Multisite environments which require HTTPS.

This is because the endpoint defers to wp_xmlrpc_server::_multisite_getUsersBlogs() on multisite which then performs a new IXR request against the current site, and IXR_Client only supports HTTP.

​https://github.com/WordPress/wordpress-develop/blob/3a730ec57c2a29765b438cc8bd9559eda2e8f648/src/wp-includes/class-wp-xmlrpc-server.php#L4847-L4856

The attached PR simply changes the code to instead call the XMLRPC method directly, rather than through an additional HTTP request, avoiding the network loopback request and removing the failure points.

Trac ticket: https://core.trac.wordpress.org/ticket/56492

[desrosj]

In 54468:

XML-RPC: Avoid loopback request in blogger.getUsersBlogs.

The blogger.getUsersBlogs endpoint does not currently work on Multisite environments which require HTTPS.

This changes wp_xmlrpc_server::_multisite_getUsersBlogs() to call the method directly instead of relying on a new IXR_Client request, which only supports HTTP.

Props dd32.
Fixes #56492.

Merged in wp_getUsersBlogs.