Add TRT RNN PID
This MR introduces the new NN-based TRT PID. The NN definition is provided by from a json file stored in the DB and interpreted by lwtnn. A new ConditionsAlg has been added to wrap lwtnn and handle the DB access. The TRTElectronPidTool is extended to calculate the NN response as an additional estimator of the electron likelihood for each track. The result is stored as additional track decoration. The old likelihood-based electron probability will still be available as alternative/fall-back.
I also took the opportunity to clean up the way the TRT track decorations are stored and passed around. In particular, the TrackSummaryTool does no longer need an instance of the dEdx-tool, since the result is already provided by the electron-probability tool.
For now the DB tag for the NN definition is forced in the job options. This can be removed once this new folder has been included in the global DB tag.
Significant work by @abayirli and @apetukho went into the preparation of this new PID method.
Fixes ATLTRTSW-48.