Bug 1095369 - Collection of Postgres table metrics fails when the tables are not in the public schema

Changed resource key format ("tablename"->"schemaname.tablename")

Implemented resource upgrade and updated resource component and discovery component

Also changed the availability check: new the resource component checks for table existence instead of looking at the parent database availability

(cherry picked from commit 835eca6a7b14bc92db5f98d336470f9b6ece145e)