Optimize string concatenation in NodeSelectionInvocationHandler.getNodeDescription()

[ori0o0p]

Replace String.join with Collectors.joining to avoid intermediate collection creation, improving performance by eliminating the unnecessary List creation step.

Make sure that:

• You have read the contribution guidelines.
• You have created a feature request first to discuss your contribution intent. Please reference the feature request ticket Performance Optimization: Replace String.join with Collectors.joining in NodeSelectionInvocationHandler.getNodeDescription #3261
• You applied code formatting rules using the mvn formatter:format target. Don't submit any formatting related changes.
• You submit test cases (unit or integration tests) that back your changes.

This optimization changes the getNodeDescription() method to use the more efficient Stream collector pattern, which directly collects stream elements into a joined string rather than first collecting to an intermediate list. While the functional outcome remains identical, this approach avoids the unnecessary memory allocation of the temporary list collection, resulting in improved performance especially in high-throughput scenarios.

The existing test suite confirms that the behavior remains consistent with the previous implementation.

Related Issue

Closes #3261

[tishun]

LGTM