IGNITE-25179 Fix AssertionError on table stopping when the colocation is enabled

[sk0x50]

https://issues.apache.org/jira/browse/IGNITE-25179

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[Copilot]

Pull Request Overview

This PR addresses the AssertionError encountered when stopping a table with colocation enabled by adjusting how null resources are handled and modifying concurrency control in the low watermark update logic.

• Replaces assertions with explicit null-checks in ZoneResourcesManager.
• Adds an assertion in PartitionReplicaLifecycleManager to catch missing zone partition resources.
• Removes write lock usage in LowWatermarkImpl during low watermark update.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
modules/partition-replicator/src/main/java/org/apache/ignite/internal/partition/replicator/ZoneResourcesManager.java	Replaces assert with null-check and annotates method return with @nullable.
modules/partition-replicator/src/main/java/org/apache/ignite/internal/partition/replicator/PartitionReplicaLifecycleManager.java	Adds an assert to verify that zone partition resources are not null before proceeding.
modules/low-watermark/src/main/java/org/apache/ignite/internal/lowwatermark/LowWatermarkImpl.java	Removes explicit locking in setLowWatermark, potentially impacting thread safety.

Comments suppressed due to low confidence (1)

modules/low-watermark/src/main/java/org/apache/ignite/internal/lowwatermark/LowWatermarkImpl.java:236

• The removal of the write lock may lead to concurrent modification issues in a multi-threaded context. Please confirm that the concurrent access to lowWatermark is correctly managed without this lock.

updateLowWatermarkLock.writeLock().lock();

[rpuch]

LGTM