Fix spacing around hidden status bar items (#39992)

This is a follow-up PR to
https://github.com/zed-industries/zed/pull/39609, and attempts to
address hidden status bar items still contributing to the layout and
creating extra spacing.

![before using display:none theres extra spaces, afterwords the buttons
are always evenly
spaced](https://github.com/user-attachments/assets/3bd07837-5f6f-4ca1-8985-9f3cb8b6893d)

- 203cbd634bfb1489b8afa4952d9594615a956b77 Adds a `.none()` method to
the `gpui::Styled` helper trait, so that status items can set their
display type to none inside their `render` method.

- 249f06e3de63b0ab32814f20e7105d8e2b642f02 Applies `.none()` to all the
status items.

- ~~499f564906c88336608c81615b11ebc9ab43d832~~ At first I was adding an
`is_visible` method to the `StatusBarView` trait, which would be used to
skip status bar items which would just render an empty div anyway, but I
felt duplicating the conditions for hiding the buttons between the
status items `is_visible` and `render` methods could be an attraction
for bugs, so I tried to find another approach. This commit contains
those changes, reverted immediately (if the `is_visible` approach is
preferred I can bring it back!)

- f37cb75f0519ceea1f3e1cc4f97087a5cb34b0fd (bonus!) Adds a condition to
the vim mode indicator to avoid a leading space when there are no
pending keys.

Release Notes:

- N/A

crates/toolchain_selector/src/active_toolchain.rs

@@ -2,12 +2,12 @@ use std::sync::Arc;
 
 use editor::Editor;
 use gpui::{
-    AsyncWindowContext, Context, Entity, IntoElement, ParentElement, Render, Subscription, Task,
-    WeakEntity, Window, div,
+    AsyncWindowContext, Context, Entity, IntoElement, ParentElement, Render, Styled, Subscription,
+    Task, WeakEntity, Window, div,
 };
 use language::{Buffer, BufferEvent, LanguageName, Toolchain, ToolchainScope};
 use project::{Project, ProjectPath, Toolchains, WorktreeId, toolchain_store::ToolchainStoreEvent};
-use ui::{Button, ButtonCommon, Clickable, FluentBuilder, LabelSize, SharedString, Tooltip};
+use ui::{Button, ButtonCommon, Clickable, LabelSize, SharedString, Tooltip};
 use util::{maybe, rel_path::RelPath};
 use workspace::{StatusItemView, Workspace, item::ItemHandle};
 
@@ -230,21 +230,22 @@ impl ActiveToolchain {
 
 impl Render for ActiveToolchain {
     fn render(&mut self, _window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
-        div().when_some(self.active_toolchain.as_ref(), |el, active_toolchain| {
-            let term = self.term.clone();
-            el.child(
-                Button::new("change-toolchain", active_toolchain.name.clone())
-                    .label_size(LabelSize::Small)
-                    .on_click(cx.listener(|this, _, window, cx| {
-                        if let Some(workspace) = this.workspace.upgrade() {
-                            workspace.update(cx, |workspace, cx| {
-                                ToolchainSelector::toggle(workspace, window, cx)
-                            });
-                        }
-                    }))
-                    .tooltip(Tooltip::text(format!("Select {}", &term))),
-            )
-        })
+        let Some(active_toolchain) = self.active_toolchain.as_ref() else {
+            return div().hidden();
+        };
+
+        div().child(
+            Button::new("change-toolchain", active_toolchain.name.clone())
+                .label_size(LabelSize::Small)
+                .on_click(cx.listener(|this, _, window, cx| {
+                    if let Some(workspace) = this.workspace.upgrade() {
+                        workspace.update(cx, |workspace, cx| {
+                            ToolchainSelector::toggle(workspace, window, cx)
+                        });
+                    }
+                }))
+                .tooltip(Tooltip::text(format!("Select {}", &self.term))),
+        )
     }
 }