fix: avoid consuming logs after client init failure

[hengyuss]

Fixes: #6846

Ensure logging clients are marked as started only after successful initialization, preventing log consumption with
uninitialized producers. Add null guards, failure cleanup, and related tests.

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• You submit test cases (unit or integration tests) that back your changes.
• Your local test passed ./mvnw clean install -Dmaven.javadoc.skip=true.

[Aias00]

Summary

Fixes #6846 — logging clients were marked started (isStarted=true) even when initClient0 failed, so consume then touched uninitialized producers/sinks and threw NPEs.

• AbstractLogConsumeClient.initClient0 return type changed from void to boolean; initClient now sets isStarted to the init result and only registers the shutdown hook when initialization succeeded.
• All 9 concrete clients (Aliyun SLS, ClickHouse, ElasticSearch, Huawei LTS, Kafka, Pulsar, RabbitMQ, RocketMQ, Tencent CLS) updated: return false on blank-config / failure (with best-effort close0() cleanup where the producer/channel was partially created), true on success.
• Added null guards in consume0 for Kafka (producer), Pulsar (producer), RabbitMQ (channel), RocketMQ (producer), Tencent CLS (client) — skip publishing with a warning instead of NPE.
• Pulsar close0 restructured so client.close() runs even if producer is null.
• New AbstractLogConsumeClientTest covers not-started-skip, started-runs, and failed-reinit leaves client stopped.

Verification

• Compile safety: grepped extends AbstractLogConsumeClient across the repo. The only extra match is AbstractLogCollector, which uses it only as a generic type bound (T extends AbstractLogConsumeClient<?, L>) — it does not override initClient0, so no missing override. All 9 real subclasses are in the diff and changed.
• Master initClient already calls this.close() when isStarted.get() before re-init; that "close previous" path is what makes testFailedReinitializationLeavesClientStopped assert closeCount==1 (init#1 starts, init#2 closes it then fails). Behavior is internally consistent.
• Existing ClickHouseLogCollectClientTest.testConsume / PulsarLogCollectClientTest.testConsume changed from expecting a thrown exception to assertDoesNotThrow — correct now that a failed init no longer marks the client started.

Conclusion

Correct, well-scoped fix with proper cleanup and good test coverage. Approving.