PluginCall final class

Calls code a plugin, theme or drop-in registered (a hook callback, a shortcode, a widget, a REST permission or field callback), as WordPress calls it. PHP judges a call's argument types by the file the call is made from: the engine's own files declare strict types, so a callback typed `int $post_id` handed the string "3494" would throw a TypeError there, where WordPress's untyped files let PHP convert it (Elementor's heartbeat passes the post ID it was posted, a string, to just such a callback). Every call into extension code is made from here, the one engine file that leaves strict types off.