Simple protocol: Send all Bootstrap when changefeed starts

[asddongmen]

Is your feature request related to a problem?

Some user requires the schema of all tables, which the changefeed synchronizes, to be sent downstream as Bootstrap events when the changefeed begins.

To fulfill this requirement, a boolean parameter send-all-bootstrap-at-start can be added, which is set to false by default.
If this parameter is set to true, the changefeed, upon starting, will send the schema of all synchronized tables downstream as Bootstrap events. This will be done synchronously in the ddlSink. After the Bootstrap events are synchronized, row changes will begin to be synchronized.

Describe the feature you'd like

as above.

Describe alternatives you've considered

No response

Teachability, Documentation, Adoption, Migration Strategy

No response