[FLINK-39076][Web UI] Display slot sharing group in operator nodes

[featzhang]

What is the purpose of the change

FLINK-39076

This change adds the ability to display the slot sharing group in operator nodes within the Flink Web UI. The slot sharing group is important for users to understand how operators are sharing slots in the TaskManager.

Brief change log

• Added slotSharingGroupId field to VerticesItem interface in job-detail.ts
• Added slotSharingGroupId property to NodeComponent in node.component.ts
• Display slot sharing group ID in operator node labels in node.component.html
• The display is conditional - only shown when slotSharingGroupId is available and the node is not pending

Verifying this change

This change can be verified by:

1. Starting a Flink job with slot sharing groups configured
2. Opening the Flink Web UI and navigating to the job's DAG view
3. Confirming that slot sharing group IDs are displayed in the operator nodes

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: no
• The S3 file system connector: no

Documentation

No documentation changes required as this is a UI enhancement.

Checklist

• The change is a proper bug fix (no).
• Docs change is needed (no, UI enhancement).
• Should this commit be backported to the release branches (no, new feature).
• Links to ASF JIRA: N/A (FLINK-XXXXX placeholder)
• How to verify this change manually (included in Verifying this change).
• How to test this change (can be verified by UI interaction).
• Documentation is needed (no).

[flinkbot]

CI report:

• ed21bc2 UNKNOWN
• 347582c Azure: FAILURE

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