* fix warnings on master
* make the `ProtoNodeIdentifier` of a Node be accessible and always a borrowed `&'static str`
* always generate `node_name::identifier()`, even with `skip_impl`
* make `FrontendNodeType` use Cow
* remove broken `DocumentNodeDefinition`s for old GPU nodes
* don't reexport `graphic_element` in it's entirety, only data structures
* adjust everything to use the new `node_name::identifier()`
* fixup imports for wasm
* turn identifier fn into a constant
* 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
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Co-authored-by: Keavon Chambers <keavon@keavon.com>
