io.shiftleft.codepropertygraph.cpgloading

Mutable data structure to preserve mapping between proto and cpg nodes during ProtoToCpg import.

Context: we need to run two passes: 1) add nodes and 2) set node properties and add edges (this is due to flatgraph-specific implementation details)

Because of that, we need to remember the mapping from proto node id to gnode. Typically, that's just a plain mapping. But there's one special case for TYPE nodes: some (parallel) frontends create duplicate TYPE nodes which we need to deduplicate...