Add languages field to GraphQL Project type

What does this MR do and why?

Implements the GET /projects/:id/languages functionality in GraphQL by adding a languages field with a corresponding RepositoryLanguage type to the Project type.

Screenshots or screen recordings

N/A

How to set up and validate locally

1. Go to http://localhost:3000/-/graphql-explorer
2. Get projects with languages

{
  projects {
    nodes {
      id
      fullPath
      languages {
        name
        share
        color
      }
    }
  }
}

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 #343063