Automatically Register Coder Scripts for startup coordination

We have implemented startup coordination using the coder exp sync commands.
This allows processes managed by a coder agent to orchestrate the order of their execution using a DAG based dependency model.

Right now, coder script resources need to explicitly execute coder exp sync in order to manage this functionality. This is a manual and error prone process.

A far better UX would be to automate the registration of coder scripts and other artefacts to the startup coordinator, such that they can depend on one another without manual registration. Once this is implemented, coder script resources would no longer have to run coder exp sync start, nor coder exp sync complete. They would however still need to run coder exp sync want.

A next step, which is beyond the scope of this issue, will be to add an attribute to Terraform that allows resources to depend on one another at runtime without any coder exp sync commands.