Add nuget allow_duplicates toggle to the group packages settings

What does this MR do and why?

In Add a setting for allowing/disallowing duplicat... (!123783 - merged), two new fields were added to the namespace's package settings:

• nuget_duplicates_allowed
• nuget_duplicate_exception_regex

In order to update their values, the user had to use the GraphQL API. In this MR, I'm adding those two fields to the packages_and_registries settings page in the UI for a specific group/namespace. So the user has the choice to whether use GraphQL API or the UI in order to update them.

Screenshots or screen recordings

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Before	After

How to set up and validate locally

When navigating to http://gdk.test:3000/groups/<group_full_path>/-/settings/packages_and_registries, you should find the NuGet duplicate setting under the Duplicate packages section as shown in the screenshot above. You can test toggling it and entering a value in the Exceptions input field.

MR acceptance checklist

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Related to #293748 (closed)