FTF seeding improvements

The main change is increasing the z vertex resolution for seeding based on vertices found by the ZFinder to from 20 mm to 150 mm for endcap layers only, and only in the jetSuper configuration. The attached plot shows that this increases the FTF tracking efficiency for tracks coming from b-hadron decays at around

|η|=2

to about the same level as without using the ZFinder, for a

t\bar{t}

sample.

Seeding using the ZFinder is still not the default in the jetSuper configuration; it's only used when flags.Trigger.InDetTracking.jetSuper.doZFinder=True, so this does not affect any default configuration.

There are also small improvements which should slightly reduce the CPU cost and memory usage of the seeding in all configurations, both with and without the ZFinder, and improve readability. The most significant one is probably bringing the processing of spacepoints from adjacent phi slices when the ZFinder is used in line with how it's done without the ZFinder: using m_phiThreeSlices instead of looping over the phi slices in createSeeds().

Tagging b-jet trigger coordinators @lshi and @lbeemste and ID trigger coordinators @sutt and @keli