Investigate project-level MR approvals to become reusable for group-level

As part of the Allow group-level MR approval rules for 'All Protected Branches' epic, we want to investigate a possibility of reusing already existing components for project-level MR approvals. There are significant similarities between existing project-level and planned group-level. But we need to map out the current implementation to know what components that come into project-level can be reusable and how the structure of ee/app/assets/javascripts/approvals/ could look like to accommodate all possible use cases.

We currently have 3 frontend issues scheduled within this epic:

1. Add FE components for group-level MR approval rules
2. Group level MR approval rules UI changes
3. Project level MR approval rules UI changes

The result of this spike should be a better refined scope and more implementation details for these issues.