core: use rounding when converting from double to long

[eckter]

This prevents off-by-one errors in the few places where we convert back and forth from one to the other. Most notably, when saving the pathfinding result in the db and re-loading it to run standalone simulations.

[codecov]

Codecov Report

Merging #5266 (e737852) into dev (e0a1bb7) will increase coverage by 0.00%.
The diff coverage is 75.00%.

@@            Coverage Diff            @@
##                dev    #5266   +/-   ##
=========================================
  Coverage     18.66%   18.66%           
- Complexity     2318     2320    +2     
=========================================
  Files           856      856           
  Lines        104007   104011    +4     
  Branches       2409     2410    +1     
=========================================
+ Hits          19409    19414    +5     
  Misses        83257    83257           
+ Partials       1341     1340    -1     

Flag	Coverage Δ
core	78.98% <75.00%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...c/main/kotlin/fr/sncf/osrd/utils/units/Distance.kt	64.51% <100.00%> (ø)
...c/main/kotlin/fr/sncf/osrd/utils/units/Duration.kt	0.00% <0.00%> (ø)
.../src/main/kotlin/fr/sncf/osrd/utils/units/Speed.kt	25.00% <50.00%> (ø)
...implementation/tracks/directed/TrackRangeView.java	86.95% <90.00%> (+0.59%)	⬆️
...va/fr/sncf/osrd/standalone_sim/SignalProjection.kt	0.00% <0.00%> (ø)

... and 1 file with indirect coverage changes