Coupon Tab access based on Promotion module

Problem/Motivation

Currently, the Coupon Tab in POS order form always showing without checking Commerce Promotion module is enabled or not. Show only the Tab if the Promotion module is enabled.

Steps to reproduce

1. Install Commerce core and Commerce POS module
2. Ensure the Commerce Promotion module is disabled
3. Goto the POS Order Form
4. You can able to see the Coupon tab without having child elements.

Proposed resolution

The check module is enabled and shows the Form fields.

Remaining tasks

User interface changes

API changes

Data model changes