Make stage placement configurable

[asafigan]

Right now the custom stage used by this plugin is set for after CoreStage::Update. For my game, I have to update some lines in CoreStage::PostUpdate after transform propagation. This causes the lines meshes to be one frame behind. I would like to make the custom stage placement configurable. I wouldn't want to change the existing interface for the plugin but I would like to add an alternative plugin which allows you to configure which stage to place the Shape stage after.

[Nilirad]

Unfortunately, current limitations of the plugin system of Bevy renders it impossible. See:

• Plugins should be more customizable and work with states bevyengine/bevy#2160

As stageless will land soon-ish, this issue will probably be resolved. You can track the progress in these places:

• ECS Mad Science Lab, stageless-ish R&D bevyengine/bevy#2801
• schedule v3 ("stageless") bevyengine/bevy#4391
• Stageless: a complete scheduling overhaul bevyengine/rfcs#45

[asafigan]

This seems to no longer be and issue on master. There is no more custom stage and instead meshes are updated after global transforms are updated in CoreStage::PostUpdate. This allowed me to place a system before meshes where updated but after global transforms are updated.