Allow admins to disable users ability to change profile name

Problem to solve

Currently, users are allowed to change their profile name and Administrators cannot prevent this action. This activity can negatively impact the integrity of audit events within GitLab. Customers need confidence their audit events are accurate (and therefore reliable) for reporting and compliance management purposes. The reliability of user identification is a key component of all compliance frameworks since an organization must be able to prove who did what.

Proposal

Provide an instance-level setting for Administrators to prevent a user from changing their profile name.

Admin Panel View	header
In Admin Panel -> Settings -> General -> Account and limit a checkbox to prevent user profile name changes.	The User Settings -> Main settings -> Full name field for User becomes read-only and cannot be changed.

• Administrators can still modify a User's name if this setting is enabled

Links / references

Related to https://gitlab.com/gitlab-org/gitlab-ce/issues/15197

Customer ticket -> https://gitlab.zendesk.com/agent/tickets/105524 (internal use)