Shaders: add BufferStruct to support bool and enums (#3109)

* node-macro: modernize `node` macro

* node-macro: add `CrateIdent` struct containing resolved crate paths

* shaders: add trait `BufferStruct` and derive macro

* shaders: `gamma_correction` and `channel_mixer` gpu nodes

* shaders: `selective_color` gpu node

* shaders: `brightness_contrast_classic` gpu node

* shaders: append GPU to display name

* node-macro: fixup doc links

* shaders: consistently append " GPU" to all shader node names

node-graph/graster-nodes/Cargo.toml

@@ -48,6 +48,7 @@ bytemuck = { workspace = true }
 glam = { workspace = true }
 spirv-std = { workspace = true }
 num-traits = { workspace = true }
+num_enum = { workspace = true }
 
 # Workspace std dependencies
 specta = { workspace = true, optional = true }