Adjust Siege-Start Banner-Placement logic to always work with a 1-chunk border

[Goosius1]

Is your feature request related to a problem? Please describe.

• Towny provinces enforces a one-chunk border
• This is convenient, because with TP + SW, with a small tweak, we can ensure non-peaceful towns can never make themselves unsiegable, thus reducing server-staff workload.

Describe the solution you'd like

• The tweak is as follows:
  • Determine the town to be attacked based on the nearest on by normal distance, to the placed banner
  • Add code to ensure that the banner cannot be captured in "safe wilderness areas":
    

Describe alternatives you've considered
N/A

Additional context
N/A