Merge RobustEndComponentDecomposition into EndComponentDecomposition

`RobustEndComponentDecomposition` is added as a part of PR https://github.com/moves-rwth/storm/pull/627 but it would be nicer if it were merged with `EndComponentDecomposition`. For iMDPs, we would have to research whether end component decomposition on iMDPs is possible in PTime (I don't know).

See the discussion: https://github.com/moves-rwth/storm/pull/627#discussion_r1897483625