Preserve physics group config with existing children

[Farley-Chen]

Summary

Preserve the provided config when creating Arcade Physics groups with existing children.

Both dynamic and static physics groups replaced the provided config when children was not a plain object or an array of plain objects. This caused options passed as the second argument to be ignored for calls like:

this.physics.add.group([sprite], {
    collideWorldBounds: true
});

this.physics.add.staticGroup([platform], config);

This change keeps the existing config object and appends the internal callbacks instead of replacing it.

Manual test

Created an Arcade Physics Group from an existing GameObject array with { collideWorldBounds: true }.

Before this change:

group.defaults.setCollideWorldBounds === false
sprite.body.collideWorldBounds === false

After this change:

group.defaults.setCollideWorldBounds === true
sprite.body.collideWorldBounds === true