use ts_ms to determine the lag between the source database update and Debezium

[lmatz]

Is your feature request related to a problem? Please describe.

Currently it is awkward to determine the lag between the source database update and Debezium.

Describe the solution you'd like

Suggested by @StrikeW

In the source object, ts_ms indicates the time that the change was made in the database. By comparing the value for payload.source.ts_ms with the value for payload.ts_ms, you can determine the lag between the source database update and Debezium.

Describe alternatives you've considered

No response

Additional context

Required by CDC testing and it also allows the user to monitor the lag between upstream DB and RW. https://github.com/risingwavelabs/risingwave-docs/issues/1513
cc: @cyliu0