Add new batch-job Bgtask service logic, and GQL API

## Motivation

- There are limitations in making the existing bgtask API handle Batch jobs without breaking compatibility, so let's create and provide a new API

## Required Features

- In the Batch job API, response formats for done, error, and partial success need to be newly defined.
- And instead of sending events for every update, let's adopt a format that periodically sends progress events at intervals of a few seconds.
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JIRA Issue: BA-2393