Add Corner to geometry and make names of corner methods consistent (#22119)

Release Notes:

- N/A

crates/collab_ui/src/collab_panel.rs

@@ -2708,7 +2708,7 @@ impl Render for CollabPanel {
                 deferred(
                     anchored()
                         .position(*position)
-                        .anchor(gpui::AnchorCorner::TopLeft)
+                        .anchor(gpui::Corner::TopLeft)
                         .child(menu.clone()),
                 )
                 .with_priority(1)

crates/collab_ui/src/collab_panel/channel_modal.rs

@@ -409,7 +409,7 @@ impl PickerDelegate for ChannelModalDelegate {
                                     Some(
                                         deferred(
                                             anchored()
-                                                .anchor(gpui::AnchorCorner::TopRight)
+                                                .anchor(gpui::Corner::TopRight)
                                                 .child(menu.clone()),
                                         )
                                         .with_priority(1),

crates/collab_ui/src/collab_ui.rs

@@ -44,7 +44,7 @@ fn notification_window_options(
     let notification_margin_height = px(-48.);
 
     let bounds = gpui::Bounds::<Pixels> {
-        origin: screen.bounds().upper_right()
+        origin: screen.bounds().top_right()
             - point(
                 size.width + notification_margin_width,
                 notification_margin_height,