Associate SSA graphnodes to their final assignment graphnode at codegen

1. Move SSA graphnode association at codegen
2. Remove this functionality from the runtime
Merge pull request #1688 from junmendoza/newMaster

Associate SSA graphnodes to their final assignment graphnode at codegen
Repro for MAGN-3576
Merge branch 'master' of https://github.com/DynamoDS/Dynamo into Recharge_Ben