CPAlgorithms: allow to write output containers that are thinned from the same source

@bdong has a use-case where a single AnaJets container is defined, and two different PtEtaSelection blocks are applied to it - defining mutually exclusive central and forward jets. The two selections are then used to create two distinct containers after Thinning is applied, which can be written to separate branches in Output.

This MR fixes a limitation of Output where the naming of an algorithm depends on the source container name, which here leads to a duplicated name error (twice AnaJets).