backend model interpreter

This will work from MetaNode or MetaNodeModel, the latter has already serialization implemented and we can re-use that for the model that will be sent to the python AST.

taken the model, iterate the map to generate mechanisms, projections and compositions in the end.
all the other steps required for the model run will be set in the end and will have to be part of the model (specific class will be required for this).

No files or tests are named. Start by comparing the MetaNode and MetaNodeModel entry points, especially the existing serialization in MetaNodeModel, then trace how the model map can produce mechanisms, projections, and compositions for the Python AST. Done means the model contains the remaining steps needed for a run and can be sent to the Python AST.

Written by the indexing model from the issue text.