[bugfix] - color overflow in get_island_colored_map

[aclegg3]

Motivation and Context

If there are more islands than pre-set colors we should invent some new ones to avoid overflow.

Also fixes a bug with the images being reflected because PIL corrdinate system is +Y downwards with origin in the top left.

How Has This Been Tested

Locally with large disjoint navmeshes.

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have completed my CLA (see CONTRIBUTING)
• I have added tests to cover my changes.
• All new and existing tests passed.

[Skylion007]

@aclegg3 We shouldn't pick a random color, we should try to pick colors that are maximally far away from each other in the appropiate colorspace like HSV. There is a nice algorithm to do this which is used for colormaps, but it's a bit tricky here since we have a manual colormap defined first and then we have to exhaust the remaining colors.