Change: Make ships smarter

[glx22]

Fixes #9566
Closes #9567

Motivation / Problem

As reported in #9566, sometimes the only valid path to the next ship destination is behind it.
It's also possible for ships to be stuck like in because they just go back on the same track when hitting a dead end.

Description

The first commit tests paths using forward and reverse direction when leaving a dock, and reverse the ship if it's the best solution.
The second commit tries all possible reverse directions when a dead end is hit.

Limitations

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, gs_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

[TrueBrain]

Sure. (I really did not understand any of it, but you are now our PF expert :P)