Add automatic type conversion and the node graph preprocessor (#2478)

* Prototype document network level into node insertion

* Implement Convert trait / node for places we can't use Into

* Add isize/usize and i128/u128 implementations for Convert trait

* Factor out substitutions into preprocessor crate

* Simplify layer node further

* Code review

* Mark preprocessed networks as generated

* Revert changes to layer node definition

* Skip generated flag for serialization

* Don't expand for tests

* Code review

---------

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

node-graph/graphene-cli/Cargo.toml

@@ -12,11 +12,7 @@ wgpu = ["wgpu-executor", "gpu", "graphene-std/wgpu"]
 wayland = ["graphene-std/wayland"]
 profiling = ["wgpu-executor/profiling"]
 passthrough = ["wgpu-executor/passthrough"]
-gpu = [
-	"interpreted-executor/gpu",
-	"graphene-std/gpu",
-	"wgpu-executor",
-]
+gpu = ["interpreted-executor/gpu", "graphene-std/gpu", "wgpu-executor"]
 
 [dependencies]
 # Local dependencies
@@ -24,6 +20,7 @@ graphene-core = { workspace = true }
 graphene-std = { workspace = true }
 interpreted-executor = { workspace = true }
 graph-craft = { workspace = true, features = ["loading"] }
+preprocessor = { workspace = true }
 
 # Workspace dependencies
 log = { workspace = true }