move NewBatchFuture API to stable workflow package

[shijiesheng]

Detailed Description
Move NewBatchFuture API out of X package.

Impact Analysis

• Backward Compatibility: breaking for x package users. This is expected since it's experimental feature
• Forward Compatibility: not applicable since it's a pure client side feature

Testing Plan

• Unit Tests: Yes but not for this pure package change particularly.
• Persistence Tests: no applicable
• Integration Tests: we have
• Compatibility Tests: it's an intended breaking change

Rollout Plan

• What is the rollout plan? Existing users will need to make code changes after upgrading it.
• Does the order of deployment matter? No
• Is it safe to rollback? Does the order of rollback matter? Yes. No
• Is there a kill switch to mitigate the impact immediately? Not needed