tests: convert tests to new style

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

tests/compute/success/overload/flat/main.cue

@@ -1,17 +1,19 @@
 package testing
 
+import "alpha.dagger.io/dagger/op"
+
 new_prop: "lala"
 #new_def: "lala"
 
 new_prop_too: string
 #new_def_too: string
 
-#up: [{
-	do:  "fetch-container"
-	ref: "busybox"
-},
-	{
-		do: "exec"
+#up: [
+	op.#FetchContainer & {
+		ref: "busybox"
+	},
+	op.#Exec & {
 		args: ["true"]
 		dir: "/"
-	}]
+	},
+]