Deprecate window creation with stale event loop

Creating window when event loop is not running generally doesn't work,
since a bunch of events and sync OS requests can't be processed. This
is also an issue on e.g. Android, since window can't be created outside
event loop easily.

Thus deprecate the window creation when event loop is not running,
as well as other resource creation to running event loop.

Given that all the examples use the bad pattern of creating the window
when event loop is not running and also most example existence is
questionable, since they show single thing and the majority of their
code is window/event loop initialization, they wore merged into
a single example 'window.rs' example that showcases very simple
application using winit.

Fixes #3399.

src/platform_impl/web/event_loop/runner.rs

@@ -214,7 +214,7 @@ impl Shared {
 
     // Set the event callback to use for the event loop runner
     // This the event callback is a fairly thin layer over the user-provided callback that closes
-    // over a RootEventLoopWindowTarget reference
+    // over a RootActiveEventLoop reference
     pub fn set_listener(&self, event_handler: Box<EventHandler>) {
         {
             let mut runner = self.0.runner.borrow_mut();
@@ -735,7 +735,7 @@ impl Shared {
         // * `self`, i.e. the item which triggered this event loop wakeup, which
         //   is usually a `wasm-bindgen` `Closure`, which will be dropped after
         //   returning to the JS glue code.
-        // * The `EventLoopWindowTarget` leaked inside `EventLoop::run` due to the
+        // * The `ActiveEventLoop` leaked inside `EventLoop::run` due to the
         //   JS exception thrown at the end.
         // * For each undropped `Window`:
         //     * The `register_redraw_request` closure.