loadtest: load test the new registry

We have recently moved the Coder registry https://registry.coder.com to a new refactored one. We would like to load test it.

It could be as simple as including some modules in the load-testing template.

```tf
module "jetbrains_gateway" {
source = "registry.coder.com/modules/jetbrains-gateway/coder"
version = "1.0.25"
agent_id = coder_agent.example.id
agent_name = "example"
folder = "/home/coder/example"
jetbrains_ides = ["CL", "GO", "IU", "PY", "WS"]
default = "GO"
}
```

cc: @bcpeinhardt to coordinate with @f0ssel when this happens. We may need to keep an eye on the registry.
Ideally, we should have monitoring #182 and #137 before we do this.