Work on integration tests

- add new entries for #70 and #74
- cleaned-up / enriched a little bit compute and exec tests

Signed-off-by: dubo-dubon-duponey <dubodubonduponey+github@pm.me>

examples/tests/exec/undefined/non_concrete_not_referenced/main.cue

@@ -0,0 +1,20 @@
+package testing
+
+hello: "world"
+bar:   string
+
+#dagger: compute: [
+	{
+		do:  "fetch-container"
+		ref: "alpine"
+	},
+	{
+		do:  "exec"
+		dir: "/"
+		args: ["sh", "-c", """
+		echo \(hello)
+		echo "This test SHOULD fail, because this script SHOULD execute, since bar is not referenced"
+		exit 1
+		"""]
+	},
+]