[Performance] Skeleton - use css contain + isolate (#29172)

## Summary & Motivation
 
as titled

## How I Tested These Changes

With only 1 tab open compare cpu/gpu usage

Before vs after
<img width="377" alt="Screenshot 2025-04-10 at 11 52 30 AM"
src="https://github.com/user-attachments/assets/6654a97e-45b3-4f7b-8efc-b9906f831267"
/><img width="365" alt="Screenshot 2025-04-10 at 12 15 46 PM"
src="https://github.com/user-attachments/assets/ef21d552-0eda-4348-a709-33a17525b91f"
/>




## Changelog

> Insert changelog entry or delete this section.

Author: salazarm

Diff for: js_modules/dagster-ui/packages/ui-components/src/components/Skeleton.tsx

@@ -11,6 +11,8 @@ export const Skeleton = styled.div<{$height?: string | number; $width?: string |
   background: ${Colors.backgroundLight()};
   position: relative;
   overflow: hidden;
+  contain: layout style size;
+  isolation: isolate;
 
   &::after {
     content: '';