Move Canvas and QRCode to iced crate

Rename `canvas` modules to `geometry` in graphics subcrates

graphics/src/geometry/style.rs

@@ -0,0 +1,23 @@
+use crate::{Color, Gradient};
+
+/// The coloring style of some drawing.
+#[derive(Debug, Clone, PartialEq)]
+pub enum Style {
+    /// A solid [`Color`].
+    Solid(Color),
+
+    /// A [`Gradient`] color.
+    Gradient(Gradient),
+}
+
+impl From<Color> for Style {
+    fn from(color: Color) -> Self {
+        Self::Solid(color)
+    }
+}
+
+impl From<Gradient> for Style {
+    fn from(gradient: Gradient) -> Self {
+        Self::Gradient(gradient)
+    }
+}