split real out into its own crate

this is a move toward reusing some of the coremem helper types in the
spirv backend.

crates/coremem/src/render.rs

@@ -6,7 +6,7 @@ use crossterm::{cursor, QueueableCommand as _};
 use crossterm::style::{style, Color, PrintStyledContent, Stylize as _};
 use font8x8::{BASIC_FONTS, GREEK_FONTS, UnicodeFonts as _};
 use log::trace;
-use num::integer::Integer;
+use num::integer::Integer;  // TODO: remove?
 use image::{RgbImage, Rgb};
 use imageproc::{pixelops, drawing};
 use rayon::prelude::*;