Fix track midpoint determination, in CGGTTS tracking

[gwbres]

• The tracking schedule and trk_midpoint are not correct in the CGGTTS Conventional Observation schedule. #285

To test the tracker, I used ./tutorials/CGGTTS/mojndnk focused on E05+E09

Results with current version:

Results with the proposal :

@vicalloy,

note that the CGGTTS scheduler is tested in cggtts/track/scheduler, for example the initial point in any day is tested thoroughly

[gwbres]

@vicalloy ,

we're locked to nyx and rtk-rs stable branches, don't forge to run a quick cargo update to make sure you collect their latest state