Allow admins to modify MR approval settings at the project-level after enabling them in admin area

Problem to solve

We implemented #39060 (closed) in %12.8, but now need to iterate on that implementation to improve a potentially-unexpected behavior. When an Administrator enables the settings in #39060 (closed) in the Admin Area, those settings are inherited by all projects in the instance. However, when an Administrator attempts to disable those settings at the project-level, the settings do not change since they are referencing the instance-level settings as a SSOT. This can be unexpected and inflexible for customers.

Intended users

• Sidney (Systems Administrator)

Proposal

We should amend our implementation of #39060 (closed) to allow Administrators to selectively toggle a setting at the project-level without being affected by the instance-level settings. Examples:

• If the instance-level settings are all enabled, an admin should be able to disable 1, 2, or all 3 of those same settings at the project level.
• If the instance-level settings are all disabled, an admin should be able to enable 1, 2, or all 3 of those same settings at the project level.

Permissions and Security

This is an improvement that affects only Administrators.