Fix #12228, Fix #12231: CheckShipReverse only restricts path when it has to

[Kuhnovic]

Motivation / Problem

Fixes #12228 and #12231

Description

Essentially a watered down version of #12335, in which I tried to fix too many things as once which caused annoying side effects.

CheckShipReverse now calls ChooseShipTrack instead of implementing a lot of the logic twice, which should make the code a bit cleaner.

Limitations

None that I'm aware of

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR touches english.txt or translations? Check the guidelines
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, game_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker