Calls mutation when dependency proxy packages settings is toggled

What does this MR do and why?

Calls mutation when dependency proxy packages settings is toggled

Updating the maven part of the form is part of subsequent MR

Adds optimistic response & cache update

Screenshots or screen recordings

Success:

Screen_Recording_2023-12-11_at_11.11.21_pm

Error:

Screen_Recording_2023-12-11_at_11.12.22_pm

How to set up and validate locally

The dependency proxy for packages has a few requirements:

1. have packages -> enabled set to true in gitlab.yml.

2. have dependency_proxy -> enabled set to true in gitlab.yml.

3. have the packages feature enabled in the project's settings. Settings -> General -> Visiblity, project features, permissions -> Package registry (checkbox enabled.)

4. have a GitLab license. Premium or more.

5. have the related feature flag turned on:

   Feature.enable(:packages_dependency_proxy_maven)

6. Visit Project > Settings > Packages and Registries

7. Click on the toggle, under the Dependency Proxy settings block.

8. Ensure the following:

   1. Toggle is updated optimistically.
   2. GraphQL request is called with the right payload & response
   3. Toast is shown indicating success/failure

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #410726 (closed)