feat(coderd/agentapi): support terraform-defined subagent ids (#21837)

Update `coderd/agentapi` to handle pre-created sub agents

coderd/database/queries/workspaceagents.sql

@@ -180,6 +180,14 @@ SET
 WHERE
 	id = $1;
 
+-- name: UpdateWorkspaceAgentDisplayAppsByID :exec
+UPDATE
+	workspace_agents
+SET
+	display_apps = $2, updated_at = $3
+WHERE
+	id = $1;
+
 -- name: GetWorkspaceAgentLogsAfter :many
 SELECT
 	*