Template selector on template approval form

Approving a template upload involves filling out both name and domain. If the template is an update to an existing one (e.g. because of a path change or missing path component), that can go wrong sometimes. For instance, if the template name is foo-bar then it's not obvious whether the domain is foo-bar or foo_bar (and in principle it could as easily be foobar or zitpick3).

It'd be helpful to show the dropdown with existing templates not just for translation files, but for templates as well. The queue reviewer could then pick an existing template there, and it would pre-fill the name and domain fields.