Add codecov yaml file (#7818)

* add codecov yaml file

* ignore storetest directory

* add a test

* relax status checks a bit for now

.codecov.yml

@@ -0,0 +1,8 @@
+coverage:
+  status:
+    project:
+      default:
+        threshold: 1%
+    patch: off
+ignore:
+  - store/storetest