Revert "windows: better looking titlebar" and follow-up (#9392)

This reverts #9053 and #9375 because they introduced a regression on
`main` that broke the titlebars on macOS:


![image](https://github.com/zed-industries/zed/assets/1185253/d046003b-5c66-4a42-9385-623f5d58c9a4)

Two things are off:

- Left padding is missing
- Titlebar height is less than it was before, which means the
traffic-light buttons are not centered vertically

What @as-cii and I noticed while looking into this: the `cfg!(macos)`
macros that were used don't work like that. You need to check for
`cfg!(target = "macos")` etc. Means that on macOS we never used the
macOS-specific code because the condition was always false.

Overall height, we're not sure about.

Release Notes:

- N/A

crates/workspace/src/workspace.rs

@@ -72,7 +72,7 @@ use task::SpawnInTerminal;
 use theme::{ActiveTheme, SystemAppearance, ThemeSettings};
 pub use toolbar::{Toolbar, ToolbarItemEvent, ToolbarItemLocation, ToolbarItemView};
 pub use ui;
-use ui::Label;
+use ui::{px, Label};
 use util::ResultExt;
 use uuid::Uuid;
 pub use workspace_settings::{AutosaveSetting, WorkspaceSettings};
@@ -4753,6 +4753,10 @@ fn parse_pixel_size_env_var(value: &str) -> Option<Size<GlobalPixels>> {
     Some(size((width as f64).into(), (height as f64).into()))
 }
 
+pub fn titlebar_height(cx: &mut WindowContext) -> Pixels {
+    (1.75 * cx.rem_size()).max(px(32.))
+}
+
 struct DisconnectedOverlay;
 
 impl Element for DisconnectedOverlay {
@@ -4766,7 +4770,7 @@ impl Element for DisconnectedOverlay {
             .bg(background)
             .absolute()
             .left_0()
-            .top(cx.titlebar_height())
+            .top(titlebar_height(cx))
             .size_full()
             .flex()
             .items_center()