Introduce `gitlab-database-load_balancing` stub

.gitlab/ci/gitlab-gems.gitlab-ci.yml

.gitlab/ci/templates/gem.gitlab-ci.yml

Gemfile.lock

gems/gem-pg.gitlab-ci.yml

gems/gitlab-database-load_balancing/.gitignore

gems/gitlab-database-load_balancing/.gitlab-ci.yml

gems/gitlab-database-load_balancing/.rspec

gems/gitlab-database-load_balancing/.rubocop.yml

gems/gitlab-database-load_balancing/Gemfile

gems/gitlab-database-load_balancing/Gemfile.lock

gems/gitlab-database-load_balancing/README.md

gems/gitlab-database-load_balancing/Rakefile

...ase-load_balancing/gitlab-database-load_balancing.gemspec

gems/gitlab-database-load_balancing/spec/spec_helper.rb

gems/gitlab-http/Gemfile.lock

gems/gitlab-rspec/Gemfile.lock

gems/gitlab-rspec/gitlab-rspec.gemspec

gems/gitlab-rspec/lib/gitlab/rspec/all.rb

gems/gitlab-rspec/lib/gitlab/rspec/stub_rails.rb

gems/gitlab-utils/Gemfile.lock