Update diff preferences dropdown
Update the settings_dropdown.vue
component (https://gitlab.com/gitlab-org/gitlab/-/blob/46415b3efe503e6dd5b719e0a3f90e71ae5273f2/app/assets/javascripts/diffs/components/settings_dropdown.vue) to match the following design:
Note the tree controls will be removed with #450833 (closed)
The main part of this is removing the segmented controller for the diff view type and instead having them as 2 different options in the dropdown with a checkmark icon