[INLONG-12010][SDK] Fix the problem of truncated string data containing Chinese characters when reporting using Dataproxy Python SDK

[yfsn666]

Fixes #12010

Motivation

When reporting a string containing Chinese characters, the length of a Chinese character in Python is 1, while the length of a Chinese character in C++ is 3, which causes the string length calculated by Python to be smaller than that in C++. Therefore, the reported length needs to be recalculated according to the C++ rules in the send() function to avoid data truncation.

Modifications

modify the inlong_dataproxy.cpp file

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

• Does this pull request introduce a new feature? no