Add logic to Projects::AllBranchesRule::MergeRequestApprovalSetting to load `approval_removals`
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In https://gitlab.com/gitlab-org/gitlab/-/issues/504615+ we created a model to store the merge request approval settings for a branch rule
As part of that change we are merging the approval removals logic so we have 1 enum instead of 2 different columns. The project settings is currently a radio select where you can chose either
1. keep all
2. remove all
3. remove the code owner approvals when code owner files change
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`Keep all` doesn't have a specific column
`Remove all` is stored in the [projects table](https://gitlab.com/gitlab-org/gitlab/-/blob/19215ebf7ec2be965582afcace84f25b10efef69/db/structure.sql#L236)
`Remove code owner approvals` is stored in the [project_settings table](https://gitlab.com/gitlab-org/gitlab/-/blob/19215ebf7ec2be965582afcace84f25b10efef69/db/structure.sql#L20023)
We need to mimic an enum value so ideally we would create the boolean methods as well as the `approval_removals` method i.e. `approval_removals_none?` `approval_removals_all?` `approval_removals_code_owner?`
issue