New Audit Event: Changes in group-level MR settings

Audit need

We currently track MR approval setting changes for projects but not for groups. Because group-level MR settings are cascaded to projects to enforce behavior, this is a critical area users need to be able to audit.

Proposal

Add audit events for all the checkboxes in the group-level MR approval settings section. Consider copying from the project-level equivalent to maintain as much consistency as possible.