Brush blend modes and erase/restore (#1261)

* Made blit node numerically stable.

* Added blend mode parameter to brush strokes.

* Fixed difference blend mode.

* Added erase/restore blend modes.

* Added blend mode and draw mode widgets.

* Added comment explaining the ImageFrame.transform.

* Initial blit/blend version.

* Working version of erase/restore.

* Improved inlining for blend functions.

* Dsiable the blend mode selector in erase/draw mode.

* Fixed incorrect bounds calculation.

* Use factor instead of percentage for opacity

* Rearrange options bar widgets

* Tidy up blend modes

* Code review

---------

Co-authored-by: Keavon Chambers <keavon@keavon.com>

node-graph/gcore/src/raster.rs

@@ -199,6 +199,7 @@ pub trait Sample {
 impl<'i, T: Sample> Sample for &'i T {
 	type Pixel = T::Pixel;
 
+	#[inline(always)]
 	fn sample(&self, pos: DVec2, area: DVec2) -> Option<Self::Pixel> {
 		(**self).sample(pos, area)
 	}