Merged requested to merge goetz/athena:SiClusterOnTrackTool_master_fix_apply_nn_splitting into master
- Support running DenseEnvironmentsAmbiguityScoreProcessorTool without a split prob tool.
- do not set split prob tool when doPixelClusterSplitting is disabled.
- respect setting of applyNNcorrection.
Also removed some dynamic casts.
Changes may help with ATLASRECTS-5544, in case NN pixel cluster splitting is really not to be used online.