SortingStoredFieldsConsumer should use a format that has better random-access

We noticed some indexing rate regressions in Elasticsearch after upgrading to a new Lucene snapshot. This is due to the fact that SortingStoredFieldsConsumer is using the default codec to write stored fields on flush. Compression doesn't matter much for this case since these are temporary files that get removed on flush after the segment is sorted anyway so we could switch to a format that has faster random access.