[vello_hybrid] Resources are now tied to Renderer instance change

This change here: https://github.com/linebender/vello/pull/1794 makes it hard to do multi threaded font rendering. I have not spent a lot of time investigating an alternate approach, but in `bevy_vello` for example we have: ```rust thread_local! { pub static LOCAL_FONT_CONTEXT: RefCell<Option<FontContext>> = const { RefCell::new(None) }; pub static LOCAL_LAYOUT_CONTEXT: RefCell<LayoutContext<Brush>> = RefCell::new(LayoutContext::new()); } ``` In my bespoke engine I _(and if bevy_vello wants to)_ use vello_hybrid instead, I had to do this and maybe still have to do: ```rust thread_local! { pub static LOCAL_FONT_CONTEXT: RefCell<Option<FontContext>> = const { RefCell::new(None) }; pub static LOCAL_LAYOUT_CONTEXT: RefCell<LayoutContext<Brush>> = RefCell::new(LayoutContext::new()); pub static LOCAL_RESOURCES: RefCell<Resources> = RefCell::new(Resources::default()); } ``` ```rust LOCAL_FONT_CONTEXT.with_borrow_mut(|font_context| { if font_context.is_none() { *font_context = Some(get_global_font_context().clone()); } let font_context = font_context.as_mut().unwrap(); LOCAL_LAYOUT_CONTEXT.with_borrow_mut(|layout_context| { self.build_layout(font_context, layout_context); LOCAL_RESOURCES.with_borrow_mut(|resources| { let mut builder = scene.glyph_run(resources, font_data); }); }); ```