Add terraform module graphql type

What does this MR do and why?

In Create packages_terraform_module_metadata table... (!141914 - merged), we introduced the database table to save the metadata of the Terraform Registry modules. Now we need to display this metadata on the UI.

To do so, we need to expose them using GraphQL APIs. In this MR, we introduce a new GraphQL type for the Terraform Registry modules' metadata. This should allow the frontend to query the details like so:

package(id:"gid://gitlab/Packages::Package/285"){
    metadata {
      ... on TerraformMetadata {
        fields {
          root {
            readmeHtml
          }
        }
      }
    }
  }
}

MR acceptance checklist

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Screenshots or screen recordings

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How to set up and validate locally

1. Publish a Terraform module. This module can be used for testing.
2. In rails console, get the global_id of the recently unloaded package/module:

   Packages::Package.terraform_module.last.to_global_id.to_s

3. In your interactive GraphQL explorer, you can test fetching the metadata using the TerraformModuleMetadata GraphQL type:

{
  package(id: "<package global_id>") {
    metadata {
      ... on TerraformModuleMetadata {
        fields {
          root {
            readmeHtml
            inputs {
              name
              type
              default
              description
            }
            outputs {
              name
              description
            }
            dependencies {
          	  modules {
                name
                source
                version
              }
              providers {
                name
                source
                version
              }
            }
            resources
          }
          submodules {
            name
            readmeHtml
            inputs {
          	name
              description
            }
            outputs {
              name
              description
            }
          }
          examples {
            name
            readmeHtml
            inputs {
          	name
              description
            }
            outputs {
              name
              description
            }
          }
        }
      }
    }
  }
}

Related to #465423 (closed)