[INLONG-11527][Agent] Save both row and byte position information when saving offset

[justinwwhuang]

Fixes #11527

Motivation

The large amount of IO required to restore historical collection sites after Agent restart results in slow startup and requires optimization

Modifications

1 Save both row and byte position information when saving offset
2 When restarting and restoring, the byte position is directly obtained from the offset information, without the need to traverse files to calculate the position

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