[Improve][Zeta] Optimize unstable CheckpointErrorRestoreEndTest cases

[Hisoka-X]

Purpose of this pull request

Optimize unstable CheckpointErrorRestoreEndTest cases. Please refer https://github.com/chestnut-c/seatunnel/actions/runs/16491224128/job/46633557547.

Does this PR introduce any user-facing change?

no

How was this patch tested?

exist test.

Check list

• If any new Jar binary package adding in your PR, please add License Notice according
  New License Guide
• If necessary, please update the documentation to describe the new feature. https://github.com/apache/seatunnel/tree/dev/docs
• If you are contributing the connector code, please check that the following files are updated:
  1. Update plugin-mapping.properties and add new connector information in it
  2. Update the pom file of seatunnel-dist
  3. Add ci label in label-scope-conf
  4. Add e2e testcase in seatunnel-e2e
  5. Update connector plugin_config

[Copilot]

Pull Request Overview

This PR optimizes the CheckpointErrorRestoreEndTest cases by replacing a non-thread-safe Integer field with an AtomicInteger to prevent race conditions in concurrent environments.

• Replace Integer pipelineRestoreNum with AtomicInteger for thread-safe counting
• Update initialization, increment, and getter operations to use atomic operations
• Maintain existing synchronization around the restore logic

[Copilot]

The increment operation is already synchronized by the restoreLock, making the atomic operation redundant. Consider using pipelineRestoreNum.incrementAndGet() or just pipelineRestoreNum++ since the synchronization block already provides thread safety.

Suggested change

	pipelineRestoreNum.getAndIncrement();
	pipelineRestoreNum++;