gpui: use a separate image in the image example and remove unnecessary examples (#8181)

Follow-up of https://github.com/zed-industries/zed/pull/8174#issuecomment-1959031659,
Fixes image example and removes window-less "noop" example.

<img width="1975" alt="Screenshot 2024-02-22 at 17 34 15"
src="https://github.com/zed-industries/zed/assets/9134003/060d8484-63b6-415a-9f06-189542422457">

Release Notes:
- N/A

crates/gpui/examples/image/image.rs

@@ -0,0 +1,73 @@
+use std::path::PathBuf;
+use std::str::FromStr;
+use std::sync::Arc;
+
+use gpui::*;
+
+#[derive(IntoElement)]
+struct ImageContainer {
+    text: SharedString,
+    src: ImageSource,
+}
+
+impl ImageContainer {
+    pub fn new(text: impl Into<SharedString>, src: impl Into<ImageSource>) -> Self {
+        Self {
+            text: text.into(),
+            src: src.into(),
+        }
+    }
+}
+
+impl RenderOnce for ImageContainer {
+    fn render(self, _: &mut WindowContext) -> impl IntoElement {
+        div().child(
+            div()
+                .flex_row()
+                .size_full()
+                .gap_4()
+                .child(self.text)
+                .child(img(self.src).w(px(512.0)).h(px(512.0))),
+        )
+    }
+}
+
+struct ImageShowcase {
+    local_resource: Arc<PathBuf>,
+    remote_resource: SharedUri,
+}
+
+impl Render for ImageShowcase {
+    fn render(&mut self, _cx: &mut ViewContext<Self>) -> impl IntoElement {
+        div()
+            .flex()
+            .flex_row()
+            .size_full()
+            .justify_center()
+            .items_center()
+            .gap_8()
+            .bg(rgb(0xFFFFFF))
+            .child(ImageContainer::new(
+                "Image loaded from a local file",
+                self.local_resource.clone(),
+            ))
+            .child(ImageContainer::new(
+                "Image loaded from a remote resource",
+                self.remote_resource.clone(),
+            ))
+    }
+}
+
+fn main() {
+    env_logger::init();
+
+    App::new().run(|cx: &mut AppContext| {
+        cx.open_window(WindowOptions::default(), |cx| {
+            cx.new_view(|_cx| ImageShowcase {
+                // Relative path to your root project path
+                local_resource: Arc::new(PathBuf::from_str("examples/image/app-icon.png").unwrap()),
+                remote_resource: "https://picsum.photos/512/512".into(),
+            })
+        });
+    });
+}