fix: remove unecessary dom re-calc in grid render (#1632)

While looking at some perf snapshots I noticed calls to
updateCanvasScale on every grid render had a ~0.25-0.5ms perf cost
(including table ticks). Mostly due to touching the dom with the set
width/set height calls triggering a recalculate style call and the
getScale call. While insignificant, it is also unnecessary unless size
actually changes. Making it conditional improves perf on most
re-renders. I used parseFloat in case grid somehow ends up with
fractional pixel if set outside of our control (which shouldn't happen,
but you never know with plugins).

Before:

![image](https://github.com/deephaven/web-client-ui/assets/1576283/2d24c2b7-cc32-409d-aa7c-4020a263cbee)

After:

![image](https://github.com/deephaven/web-client-ui/assets/1576283/b2fe80ce-354a-47d1-a788-6abb071c462d)
updateCanvasScale is now gone from the perf profile entirely on a normal
grid render.

Tested re-sizeing panels, and window with table both shown and hidden
still resizes grid correctly.

packages/grid/src/Grid.tsx

@@ -824,14 +824,23 @@ class Grid extends PureComponent<GridProps, GridState> {
     if (!canvasContext) throw new Error('canvasContext not set');
     if (!canvasWrapper.current) throw new Error('canvasWrapper not set');
 
-    const scale = Grid.getScale(canvasContext);
     // the parent wrapper has 100% width/height, and is used for determining size
     // we don't want to stretch the canvas to 100%, to avoid fractional pixels.
     // A wrapper element must be used for sizing, and canvas size must be
     // set manually to a floored value in css and a scaled value in width/height
     const rect = canvasWrapper.current.getBoundingClientRect();
     const width = Math.floor(rect.width);
     const height = Math.floor(rect.height);
+
+    // avoid triggering a dom re-calc if size hasn't changed
+    if (
+      parseFloat(canvas.style.width) === width &&
+      parseFloat(canvas.style.height) === height
+    ) {
+      return;
+    }
+
+    const scale = Grid.getScale(canvasContext);
     canvas.style.width = `${width}px`;
     canvas.style.height = `${height}px`;
     canvas.width = width * scale;