Adding RNN based TauTrack selection using a custom lwtnn implementation

This MR includes new TauTrackRNNClassifier and TauTrackRNN classes implementing RNN based tau track selection. The package requires a subset of lwtnn to be compiled within tauRecTools since we need a new internal state forwarding feature. Headers and source are located in tauRecTools/lwtnn/.h and Root/lwtnn/.cxx. These changes in the lwtDev namespace to not interfere with the atlas implementation of lwtnn (namespace lwt).

As a long term goal lwtnn will adopt the new features so the internal version can be removed. (See https://its.cern.ch/jira/browse/AML-10)