ATLASRECTS-5750: Add faster version of lwtnn
The calls to std::map<std::string,double> were slowing things down quite a bit in the track ambiguity solver. This merge request introduces a variant of LightweightGraph called FastGraph which takes Eigen::VectorXd and Eigen::MatrixXd type inputs and returns Eigen::VectorXd. Hopefully this will speed things up.
After this one, !38018 (merged) can be merged.
Edited by Gabriel Facini