Track extension tool

This tool implements the track extension as done for the HGTD TDR results, but utilising the new infrastructures available in 21.9.

I have iterated with @ncalace to get the selection of surfaces etc set up (thanks!). There is a lot of manual selection happening currently as I explained in the software integration meeting, this can be improved in the future.

Tagging @cohm @dshope @vraskina @sch @wyswys for info as well as @tstreble @asalzbur @npetters @nstyles for possible additional feedback!