Improve Issue Split Function

Summary

Currently, if users use any validator in Create transition which set required field and tried to split issue, the action will fail.

Steps to reproduce

1. Install JIRA Suite Utitlies
2. Edit workflow of any project and edit the Create transition.
3. In the Create transition, add a validator that set specific field as required.
4. Go to board and try to split issues from backlog.

By default, JIRA only ship with the following 2 validators for Create transition:

Permission Validator
User Permission Validator

Split feature fails since the required feature is part of third party plugin.

Environment

JIRA 7.6.2, JIRA 7.7.0

Expected Results

Split feature creates new issue while copying the required field from the parent issue.

Actual Results

Split feature fails to create new issue due to the missing required field value.

Workaround

None.