Refactor Perturbative_Interface with factorised approach using `Cluster_Amplitude`
Shower input defined by Cluster_Amplitude attached to pre-created shower blob with all "incoming" particles.
Decay_Cascade will amend Cluster_Amplitude and blob according to decay legs
Perturbative_Interface is removed, LocalKFactor can go into Matrix_Element_Handler
Jet_Evolution iterates over blobs and starts Shower_Handler for each status::needs_showers blob (with its cluster amplitude attached). At the end, collects particles from Cluster_Amplitude and adds them to blob.
sets blob_status::needs_hadronization for shower blob
Potential shower input sources that would create the blob and attach a Cluster_Amplitude:
