codecov: enable status for patch/changes, comment: diff (#6080)

Ref: #6077 (comment)

This is #6050
without the project status, and fixes/improves the comment added in
#6077.

Author: blueyed

codecov.yml

@@ -1,8 +1,8 @@
 coverage:
   status:
     project: false
-    patch: false
-    changes: false
+    patch: true
+    changes: true
 
 comment:
-  layout: "reach"
+  layout: "diff"