Ensure panel and pane sizes are integral (#8619)

Fixes: #8050

For some reason that we didn't investigate, if you have view caching
enabled,
and you have non-integer sized bounds, and you are right aligning
things, the
co-ordinates can differ by +/- 1px when using the cached view.

The easiest fix for now is to just not do that.

Co-Authored-By: Antonio <as-cii@zed.dev>

Release Notes:

- Fixed the pane icons flickering
([#8050](https://github.com/zed-industries/zed/issues/8050)).

Co-authored-by: Antonio <as-cii@zed.dev>

crates/workspace/src/dock.rs

@@ -522,7 +522,7 @@ impl Dock {
 
     pub fn resize_active_panel(&mut self, size: Option<Pixels>, cx: &mut ViewContext<Self>) {
         if let Some(entry) = self.panel_entries.get_mut(self.active_panel_index) {
-            let size = size.map(|size| size.max(RESIZE_HANDLE_SIZE));
+            let size = size.map(|size| size.max(RESIZE_HANDLE_SIZE).round());
             entry.panel.set_size(size, cx);
             cx.notify();
         }

crates/workspace/src/pane_group.rs

@@ -883,7 +883,8 @@ mod element {
 
                 let child_size = bounds
                     .size
-                    .apply_along(self.axis, |_| space_per_flex * child_flex);
+                    .apply_along(self.axis, |_| space_per_flex * child_flex)
+                    .map(|d| d.round());
 
                 let child_bounds = Bounds {
                     origin,