Implement correct planet size calculation when creating a new planet

[lanedirt]

Currently when a new planet is created a random planet size is chosen based on this logic in PlanetServiceFactory::createPlanet():

        $planet->field_max = rand(140, 250);

So currently the planet size is fully random and does not take into account any other information.

The official game however implements certain rules for a small or big a planet can become based on the position of the planet. Up-to-date information can be found here: https://ogame.fandom.com/wiki/Planet_Size.

Todo:

• Change the planet size calculation logic to conform to how the official game works.

[lanedirt]

Fixed by #507.