Reflection - Add a way to register or modify RequiredComponents for a component whose type you don't know

[makspll]

What problem does this solve or what need does it fill?

Currently you can:

• register a dynamic component with World::register_component_with_descriptor
• register required components for a component whose type you know at compile time via: World::register_required_components()
• retrieve a &RequiredComponents for any component
• Create a new component implementing type which initializes its RequiredComponents BUT PURELY with compile time information i.e. no &self

But there is no way to either (as far I can see):

• initialize your dynamic component with a specific RequiredComponents
• retrieve a &mut for the components RequiredComponents after the fact

What solution would you like?

• Add ability to get to &mut RequiredComponents for any component
• Add &self to Component::register_required_components
• Add RequiredComponents argument to register_component_with_descriptor or an alternative function with that argument

What alternative(s) have you considered?

• Perhaps there is a horribly cursed way to do this if you pass the required components via World through a resource or something, but even that seems difficult as there's no way to call register_required_components yourself.
• An ability to create a component with a custom ComponentInfo yourself