feat(server): report apisix-standalone endpoint status

[bzp2010]

Description

When syncing to the apisix-standalone backend on the ADC server mode, report additional endpoint status information.

BREAK CHANGE:

Only for apisix-standalone backend, neither related to apisix nor api7ee

• All apisix-standalone endpoint statuses are now reported via the endpoint_status field instead of the previously used success and failed fields.

• failed will always be an empty array.

• success contains records generated by the diff returns events. However, you should not assume all synchronizations succeeded based on this; the synchronization status is confirmed by the success_count, failed_count, status, and endpoint_status values.

• total_resources will always be 0.

• status, success_count, and failed_count reflect the synchronization status on the endpoint.

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible