Bump @actions/cache to 5.1.0, log cache write denied (#758)

* Bump @actions/cache to 5.1.0, log cache write denied

* Add cache save tests

* Re-trigger CI

.licenses/npm/@actions/cache.dep.yml

@@ -1,6 +1,6 @@
 ---
 name: "@actions/cache"
-version: 5.0.5
+version: 5.1.0
 type: npm
 summary: Actions cache lib
 homepage: https://github.com/actions/toolkit/tree/main/packages/cache