[INLONG-11175][Agent] Fix the problem of mqttsource message loss

[qy-liuhuo]

Fixes #11175

Due to the timeout mechanism of blocking queue offers（mqttMessagesQueue.offer(new DefaultMessage(recordValue, headerMap), 1, TimeUnit.SECONDS);）, messages may be lost when the queue is full

Motivation

Removed the timeout setting for offer operation in the MqttSource file， When the queue is full, the offer operation will be blocked until there is free space in the queue, thus avoiding the problem of messages being discarded.

Modifications

Verifying this change

(Please pick either of the following options)

• This change is a trivial rework/code cleanup without any test coverage.

• This change is already covered by existing tests, such as:
  (please describe tests)

• This change added tests and can be verified as follows:

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  • Added integration tests for end-to-end deployment with large payloads (10MB)
  • Extended integration test for recovery after broker failure

Documentation

• Does this pull request introduce a new feature? (yes / no)
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