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/project_panel/src/project_panel.rs

@@ -338,7 +338,7 @@ impl ProjectPanel {
             let panel = ProjectPanel::new(workspace, cx);
             if let Some(serialized_panel) = serialized_panel {
                 panel.update(cx, |panel, cx| {
-                    panel.width = serialized_panel.width;
+                    panel.width = serialized_panel.width.map(|px| px.round());
                     cx.notify();
                 });
             }