cdc: Changefeed export does not correctly update schedule

Changefeed job started by scheduled changefeed does not correctly
update schedule information upon completion. When terminated w/out
an error, we want to update schedule metrics; if terminated with an error,
we should retry based on the schedule behavior.

Jira issue: CRDB-31620

No files, tests, or entry points are named. Start by tracing how a scheduled changefeed job completes and updates schedule information, then inspect the schedule behavior for successful termination and error retry handling. Done means successful jobs update schedule metrics and failed jobs retry according to the schedule behavior.

Written by the indexing model from the issue text.