Improve API Ergonomics

Ideally the following function wouldn't have to be called by the user and could be called internally. It is currently necessary due to possibly needing access to the context in order to resize the glyph cache texture when it becomes too small to fit additional glyphs. The context is unavailable during rendering as the surface type which implements GraphicsContext will be in a borrowed state from building the pipeline.

luminance-glyph/src/lib.rs

Lines 213 to 216 in 651678b

    
           pub fn process_queued<C>(&mut self, context: &mut C) 
        
           where 
        
               C: GraphicsContext, 
        
           {

	pub fn process_queued<C>(&mut self, context: &mut C)
	where
	C: GraphicsContext,
	{