refactor(plexus): migrate Node to functional component (#3392) (#3531)

## Which problem is this PR solving?

- Resolves #3392

## Description of the changes

- Migrated the `Node` component from a class-based component to a
functional component with `React.memo()`
- Converted `Node` class component extending `React.PureComponent` to a
functional component
- Wrapped the component with `React.memo()` to preserve the shallow prop
comparison behavior of `PureComponent`
- Destructured props directly in the function signature
- Removed the `render()` method and converted to direct return statement
- Maintained generic type support using double type assertion pattern:
`as unknown as <T = {}>(props: TProps<T>) => React.ReactElement | null`
- Preserved all existing functionality including conditional rendering
logic
- No changes to component logic or behavior, only structural refactoring

## How was this change tested?

- All existing plexus tests pass (18 tests)
- TypeScript compilation successful
- Prettier formatting verified
- Build successful for plexus package
- Minimal diff: 18 insertions, 18 deletions

## Proof - 
<img width="367" height="123" alt="3392 proof"
src="https://github.com/user-attachments/assets/85bdb61c-d456-4d66-a121-090e7ee4c11c"
/>


## Checklist

- [x] I have read
https://github.com/jaegertracing/jaeger/blob/main/CONTRIBUTING_GUIDELINES.md
- [x] I have signed all commits
- [x] I have added unit tests for the new functionality
- [x] I have run lint and test steps successfully: `make lint test`

## AI Usage in this PR (choose one)

See [AI Usage
Policy](https://github.com/jaegertracing/jaeger/blob/main/CONTRIBUTING_GUIDELINES.md#ai-usage-policy).

- [ ] **None**: No AI tools were used in creating this PR
- [ ] **Light**: AI provided minor assistance (formatting, simple
suggestions)
- [x] **Moderate**: AI helped with code generation or debugging specific
parts
- [ ] **Heavy**: AI generated most or all of the code changes

Signed-off-by: hharshhsaini <sainiharsh3311@gmail.com>

Author: hharshhsaini

packages/plexus/src/Digraph/Node.tsx

@@ -26,23 +26,23 @@ function getHtmlStyle(lv: TLayoutVertex<any>) {
   };
 }
 
-export default class Node<T = {}> extends React.PureComponent<TProps<T>> {
-  render() {
-    const { getClassName, layerType, renderNode, renderUtils, setOnNode, layoutVertex } = this.props;
-    const nodeContent = renderNode(layoutVertex, renderUtils);
-    if (!nodeContent) {
-      return null;
-    }
-    const { left, top } = layoutVertex;
-    const props = assignMergeCss(
-      {
-        className: getClassName('Node'),
-        style: layerType === ELayerType.Html ? getHtmlStyle(layoutVertex) : null,
-        transform: layerType === ELayerType.Svg ? `translate(${left.toFixed()},${top.toFixed()})` : null,
-      },
-      getProps(setOnNode, layoutVertex, renderUtils)
-    );
-    const Wrapper = layerType === ELayerType.Html ? 'div' : 'g';
-    return <Wrapper {...props}>{nodeContent}</Wrapper>;
+function Node<T = {}>(props: TProps<T>) {
+  const { getClassName, layerType, renderNode, renderUtils, setOnNode, layoutVertex } = props;
+  const nodeContent = renderNode(layoutVertex, renderUtils);
+  if (!nodeContent) {
+    return null;
   }
+  const { left, top } = layoutVertex;
+  const nodeProps = assignMergeCss(
+    {
+      className: getClassName('Node'),
+      style: layerType === ELayerType.Html ? getHtmlStyle(layoutVertex) : null,
+      transform: layerType === ELayerType.Svg ? `translate(${left.toFixed()},${top.toFixed()})` : null,
+    },
+    getProps(setOnNode, layoutVertex, renderUtils)
+  );
+  const Wrapper = layerType === ELayerType.Html ? 'div' : 'g';
+  return <Wrapper {...nodeProps}>{nodeContent}</Wrapper>;
 }
+
+export default React.memo(Node) as typeof Node;