Add LoC count to the Repository Analytics UI

Part of epic: &9692

After #388918 is completed.

Problem

#388918 introduced a new field (LoC count) in CommitLanguages RPC. We need to display this data on UI.

Proposal

• Fetch the LoC data from CommitLanguages RPC
• Add this data to Ruby methods (consult with frontend devs):
  • https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/helpers/repository_languages_helper.rb
  • https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/views/projects/graphs/charts.html.haml