Adding a prefix to the LLP1 and SUSY20 track/calo isolation variables, JIRA: ATLASG-2690

This request adds the prefix LLP1_ (SUSY20_) to the name of track isolation variables in the LLP1 (SUSY20) format. This resolves the conflict of the calo isolation variables of the LLP1 format using the IsolationTrackDecorator and the muon isolation variables. The treatment for SUSY20 can prevent conflicts in the future when the calo isolation variables are going to be implemented. tag: @isiral, @tstreble, @alsala