Add History type and merge-commit model to graph-storage (#4238)

* Add History type and merge-commit model to graph-storage

* Add History::merge with canonical-sort convergence to graph-storage

* Append merge delta without re-sorting the whole history

* Resurrect across merges by searching all ancestors, not the primary chain

document/graph-storage/src/lib.rs

@@ -4,6 +4,7 @@ pub mod attributes;
 pub mod crdt;
 pub mod delta;
 pub mod document;
+pub mod history;
 pub mod ids;
 pub mod model;
 pub mod registry;
@@ -21,6 +22,7 @@ pub use attributes::*;
 pub use crdt::*;
 pub use document::*;
 pub use from_runtime::{RuntimeConversion, decode_declaration, encode_declaration};
+pub use history::History;
 pub use ids::*;
 pub use metadata_source::{InputMetadataEntry, NetworkMetadataEntry, NoMetadata, NodeMetadataEntry, NodeMetadataSource, Position};
 pub use model::*;