Group Relationships are not removed when Group is deleted

Problem/Motivation

When deleting a group, the groups relationships within the group_relationship and group_relationship_field_data tables are not removed. This causes issues when using the group.membership_loader service outside of the group module, as the membership relationship still exists, but the group ID from the relationship can no longer be found as a group entity. A user should not have to remove relationships tied to a group prior to deleting the group.

Steps to reproduce

• Create Group
• Add some memberships
• See that relationships were added in the database tables referenced
• Delete group
• Relationships should still exist within these tables

Proposed resolution

Upon deletion of the group, rows that have a corresponding gid in table group_relationship_field_data should be removed, along with their corresponding id in the group_relationship table, and any other related data that I may have overlooked.