Improve usability of `PlayerSettingsSetIconsTask`

[ruccho]

Currently PlayerSettingsSetIconsTask simply exposes PlayerSettings.SetIcons() but it provides difficult user interface to understand.

public static void SetIcons(NamedBuildTarget buildTarget, Texture2D[] icons, IconKind kind);

The list is the same length as the list of icon sizes returned by GetIconSizes.

https://docs.unity3d.com/6000.0/Documentation/ScriptReference/PlayerSettings.SetIcons.html