Migrate all starter templates from `coder/coder` to new Hub repo

[Parkreiner]

This is part of #530.

This should be far less involved compared to migrating the modules from the Modules repo. We do have a separate coder/templates repo, but that was never made public. The Registry also pulls all its current templates from coder/coder as well. This setup means that we would be able to dump all current templates into the Hub's /coder user subdirectory and call it a day. It's probably worth asking which templates are the most up-to-date between coder/coder and coder/templates, but that would be the main source of ambiguity.

For better or worse, the templates don't currently have any tests in place, so that makes migrating them even easier.