Introduce Split/Combine Channels nodes (#1153)

* Add Channel Extrataction Node

* Add hacky BlendModes for Inserting Color Channels

* Fix Channel Exporter

* Add Monochrome Option and Multi Output Node

* Fix Input Mapping

* Fix Formatting

* Split Alpha Extraction to seperate node

* Remove unnecessary functionality

* Add Alpha Channel as an output to the extract channel node

* Fix compilation

* Add unpolished 'Combine Channels' Node

* Fix Rebasing Issues

* Add a bit of polish

* Fix Rebase Issues

* Switch from 'ColorChannel' to 'RedGreenBlue'
I initially added an enum to hold color channels called 'ColorChannel', but while implementing the nodes, there somebody allready added a similar enum so I switched to that type

* Add correct names

* Add Improvement

- Some Performance Improvements
- Some Formatting Improvements

* Add some improvements
Most of this stuff was done by TrueDoctor in my Luchbreak :D

* Implement IO Improvements
- Converted primary output from split node to a dummy output
- Removed primary Input from split node

* Fix Formatting

* Fix Combine RGB Node (hopefully final :D )

* Swap around Inputs and Outputs
Move from ARGB -> RGBA

* Improve naming

* More naming fixes

* Fix Replace -> Into

* Rename Replacment -> Insertion

* Add blank assist area

---------

Co-authored-by: Keavon Chambers <keavon@keavon.com>
Co-authored-by: Dennis Kobert <dennis@kobert.dev>

node-graph/gcore/src/raster.rs

@@ -140,6 +140,11 @@ pub trait RGB: Pixel {
 		self.blue()
 	}
 }
+pub trait RGBMut: RGB {
+	fn set_red(&mut self, red: Self::ColorChannel);
+	fn set_green(&mut self, green: Self::ColorChannel);
+	fn set_blue(&mut self, blue: Self::ColorChannel);
+}
 
 pub trait AssociatedAlpha: RGB + Alpha {
 	fn to_unassociated<Out: UnassociatedAlpha>(&self) -> Out;