Hide issue contacts and quick actions

What does this MR do and why?

Related to #349765 (closed)

This MR hides the contacts sidebar widget for issues in groups with no contact. It also hides the /add_contacts and /remove_contacts quick actions

Screenshots or screen recordings

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

0. Enable :customer_relations feature flag for a group via the rails console
1. Visit a group settings page (e.g. http://gdk.test:3000/groups/flightjs/-/edit
2. Expand "Permissions and group features"
3. At the very bottom, select "Enable customer relations"
4. Select "Save changes"
5. Navigate to an issue in the group
6. You should not see the contacts widget in the sidebar and the "/add_contacts" and "/remove_contacts" quick actions should not be available
7. Visit the customer relations > contacts page for the group (e.g. http://gdk.test:3000/groups/flightjs/-/crm/contacts
8. Create a new contact
9. Navigate to an issue in the group
10. You should now see the contacts widget in the sidebar and the "/add_contacts" and "/remove_contacts" quick actions should be available

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.