Add option to change color of the turns arrow in the Route line settings

[anastasiia936]

In some map modes default color become invisible:

[Nine-Tailed]

In my opinion it is better to add a contour line at the turns arrows.

[dmpr0]

[vshcherb]

We should have automatic alternate color for a given color if distance between current route segment color too close - same should be applied to route direction arrows

[vshcherb]

There should be a formula to check contrast ration - https://stackoverflow.com/questions/22031644/formula-for-contrast-ratio-threshold-in-cielab-space - alternate color could be just opposite by hsv.

[vshcherb]

Bugs mentionned on demo

[DmitryAlexei]

OsmAnd~ 4.6.0#710m, released: 2023-09-01

• there is no option to change color of the turns arrows in the Route line settings (Navigation > Navigation settings > Customise route line). Their color is changed automatically.
• turn arrows are good seen when their width is set to medium or bold in day and night modes and styles

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