Fix focus handle leak (#26090)

This fixes a major performance issue in the current git beta.
This PR also removes the PopoverButton component, which was easy to
misuse.

Release Notes:

- Git Beta: Fix frame drops caused by opening the git panel

---------

Co-authored-by: Mikayla Maki <mikayla.c.maki@gmail.com>

crates/ui/src/components/popover_button.rs

@@ -1,57 +0,0 @@
-use gpui::{AnyView, Corner, Entity, ManagedView};
-
-use crate::{prelude::*, PopoverMenu, PopoverMenuHandle, PopoverTrigger};
-
-pub trait TriggerablePopover: ManagedView {
-    fn menu_handle(
-        &mut self,
-        window: &mut Window,
-        cx: &mut gpui::Context<Self>,
-    ) -> PopoverMenuHandle<Self>;
-}
-
-pub struct PopoverButton<T, B, F> {
-    selector: Entity<T>,
-    button: B,
-    tooltip: F,
-    corner: Corner,
-}
-
-impl<T, B, F> PopoverButton<T, B, F> {
-    pub fn new(selector: Entity<T>, corner: Corner, button: B, tooltip: F) -> Self
-    where
-        F: Fn(&mut Window, &mut App) -> AnyView + 'static,
-    {
-        Self {
-            selector,
-            button,
-            tooltip,
-            corner,
-        }
-    }
-}
-
-impl<T: TriggerablePopover, B: PopoverTrigger + ButtonCommon, F> RenderOnce
-    for PopoverButton<T, B, F>
-where
-    F: Fn(&mut Window, &mut App) -> AnyView + 'static,
-{
-    fn render(self, window: &mut Window, cx: &mut App) -> impl IntoElement {
-        let menu_handle = self
-            .selector
-            .update(cx, |selector, cx| selector.menu_handle(window, cx));
-
-        PopoverMenu::new("popover-button")
-            .menu({
-                let selector = self.selector.clone();
-                move |_window, _cx| Some(selector.clone())
-            })
-            .trigger_with_tooltip(self.button, self.tooltip)
-            .anchor(self.corner)
-            .with_handle(menu_handle)
-            .offset(gpui::Point {
-                x: px(0.0),
-                y: px(-2.0),
-            })
-    }
-}