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/node-macro/Cargo.toml

@@ -27,3 +27,4 @@ proc-macro-error2 = "2"
 
 [dev-dependencies]
 graphene-core = { workspace = true }
+graphene-core-shaders = { workspace = true }