CI: different pipelines for this repo and generated templates

* It doesn't seem to make much sense to deploy the template to gitpod.
~~* It would make sense to set up some automatic testing of the template (generate a template -> run a bunch of commands like `cargo test`, `cargo schema`, etc).~~

At a glance, it looks like this might be possible with pre-hooks:

https://cargo-generate.github.io/cargo-generate/templates/scripting.html

Start with the cargo-generate scripting and pre-hooks documentation linked in the issue, then inspect this repository's existing CI and template-generation flow. Determine how separate pipelines should treat the repository and generated templates, including the mentioned cargo test and cargo schema commands; done means the intended CI behavior is automated and documented.

Written by the indexing model from the issue text.