Moving a JsObject inside a closure causes a panic

[jedel1043]

Describe the bug
Currently moving any Gc<T> inside a closure causes a panic. This issue comes from Manishearth/rust-gc#50, and it doesn't seem like it will get fixed until there's some API for garbage collectors in rustc.
However, we currently allow moving JsObjects and JsValues inside closures, which causes a panic on destruction.

To Reproduce

use boa::{Context, JsValue};

fn main() -> Result<(), JsValue> {
    let mut context = Context::new();

    let object = context.construct_object();

    let moved_object = object.clone();

    context.register_global_closure("closure", 0, move |_, _, _| {
        // This value is captured from main function.
        moved_object.is_array();
        Ok(JsValue::Undefined)
    })?;

    Ok(())
}

Additional comments
Should we restrict closures to only Fn(..) + Copy? Or should we allow any Fn and document that moving a JsObject into a closure causes a panic?
Maybe we could even make all closures Fn(..) + Copy and ask the user to pass a Captures type, then we change the definition of our closures to Fn(&JsValue, &[JsValue], &mut Closure, Box<dyn Any>) and ask the user to downcast the dyn Any to the type of its Captures. This allows maximum flexibility because the user can pass JsValue and JsObject, but it's also not very ergonomic.

[Razican]

@HalidOdat does it make sense to not have the register_global_closure() API for 0.13?

[jedel1043]

I forgot to mention this blocks the implementation of Arguments Mapped exotic objects, because to create one we need to capture the current Environment in a closure and save that closure inside the object.