Refactor Windows platform implementation (#11393)

This aligns the Windows platform implementation with a code style
similar to macOS platform, eliminating most of the `Cell`s and
`Mutex`es. This adjustment facilitates potential future porting to a
multi-threaded implementation if required.

Overall, this PR made the following changes: it segregated all member
variables in `WindowsPlatform` and `WindowsWindow`, grouping together
variables that remain constant throughout the entire app lifecycle,
while placing variables that may change during app runtime into
`RefCell`.

Edit: 
During the code refactoring process, a bug was also fixed.

**Before**: 
Close window when file has changed, nothing happen:


https://github.com/zed-industries/zed/assets/14981363/0bcda7c1-808c-4b36-8953-a3a3365a314e

**After**:
Now `should_close` callback is properly handled


https://github.com/zed-industries/zed/assets/14981363/c8887b72-9a0b-42ad-b9ab-7d0775d843f5


Release Notes:

- N/A

crates/gpui/src/platform/windows/util.rs

@@ -74,6 +74,7 @@ pub(crate) unsafe fn set_window_long(
     }
 }
 
+#[derive(Debug, Clone)]
 pub(crate) struct OwnedHandle(HANDLE);
 
 impl OwnedHandle {
@@ -135,3 +136,19 @@ pub(crate) fn load_cursor(style: CursorStyle) -> HCURSOR {
         )
     })
 }
+
+#[inline]
+pub(crate) fn logical_size(physical_size: Size<DevicePixels>, scale_factor: f32) -> Size<Pixels> {
+    Size {
+        width: px(physical_size.width.0 as f32 / scale_factor),
+        height: px(physical_size.height.0 as f32 / scale_factor),
+    }
+}
+
+#[inline]
+pub(crate) fn logical_point(x: f32, y: f32, scale_factor: f32) -> Point<Pixels> {
+    Point {
+        x: px(x / scale_factor),
+        y: px(y / scale_factor),
+    }
+}