add new index for performin getStepMetada method and use productionoutputfiles table instead of jobs and files

When a dataset is saved from the WUI, each step and its metadata also saved together with the lfns. Most of the case when the dataset is MC then the last step does not contains DDDB, CONDB tags instead 'fromPreviousStep' is used. Consequently, we have to get the tags from the ancestors. In order to do that we used the jobs and files tables, which some cases the queries were slow (~1 minutes or even more). As we introduced the productionoutputfiles (note the previous MV only contained the datasets ReplicaFlag='Yes' and VisibilityFlag='Y') table, which contains each production and all relevant metadata we can use this table to get the ancestors of a certain production.