Switch CD applications query to organization-level

What does this MR do and why?

Update the cd_applications GraphQL query and the components that consume it to fetch applications directly from the organization, instead of through organization.groups.cdApplications.

This unblocks !240565 (merged), which removes the group surface from the CD GraphQL API to support organization-only ownership. Without this MR, the GraphQL query validation job in !240565 (merged) fails with Field 'cdApplications' doesn't exist on type 'Group'.

References

• https://gitlab.com/gitlab-org/gitlab/-/work_items/602765#note_3454308724
• https://gitlab.com/gitlab-org/gitlab/-/work_items/602765

Screenshots or screen recordings

How to set up and validate locally

1. Enable the ai_native_deploy and ui_for_organizations feature flags.
2. Create an application that belongs to an organization.

mutation {
  cdApplicationCreate(input: {
    organizationId: "gid://gitlab/Organizations::Organization/1",
    name: "payments-app",
    description: "Payments App",
  }) {
    application {
      id
      name
      description
      organization {
        id
        name
      }
    }
    errors
  }
}

4. Navigate to http://127.0.0.1:3000/o/default/-/deploy/applications to view a list of applications, including the newly created application.

MR acceptance checklist

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