IGNITE-27521 Java client: handle multiple endpoints for the same node

[ptupitsyn]

https://issues.apache.org/jira/browse/IGNITE-27521

[Copilot]

Pull request overview

This PR addresses IGNITE-27521 by improving the Java thin client behavior when multiple distinct endpoints resolve to the same server node, adding a warning and extending test coverage for the scenario.

Changes:

• Add a warning log when different endpoints connect to the same server node.
• Update connections() reporting to reflect multiple active endpoint connections to the same node (while skipping duplicate-config weights).
• Add a new DNS discovery test that asserts the warning is logged and that both connections are tracked and closed.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
modules/client/src/test/java/org/apache/ignite/client/ClientDnsDiscoveryTest.java	Adds a new test for “multiple endpoints -> same node” and wires a test logger into client configuration.
modules/client/src/main/java/org/apache/ignite/internal/client/ReliableChannel.java	Emits a warning on multi-endpoint-to-same-node detection and adjusts connections() to enumerate per-endpoint holders.

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