This change adds support for devcontainer autostart in workspaces. The
preconditions for utilizing this feature are:

1. The `coder_devcontainer` resource must be defined in Terraform
2. By the time the startup scripts have completed,
	- The `@devcontainers/cli` tool must be installed
	- The given workspace folder must contain a devcontainer configuration

Example Terraform:

```tf
resource "coder_devcontainer" "coder" {
  agent_id         = coder_agent.main.id
  workspace_folder = "/home/coder/coder"
  config_path      = ".devcontainer/devcontainer.json" # (optional)
}
```

Closes #16423