[INLONG-11145][Agent] Optimize the logic of supplementing data

[justinwwhuang]

Fixes #11145

Motivation

The logic for supplementing data needs to be optimized to prevent data loss

Modifications

1. If the action queue is full, the action cannot be directly discarded
2. Determination of completion of supplementary data task: The number of scanned files is equal to the number of collected files

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:

  (example:)

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

Documentation

No doc needed