Improve Aggregation

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This MR improves a few this in the Aggregation pass :

• Use of add_prefix and internal_get_name_and_counter which should be avoided.
• Scope data are stored in a map for faster lock up
• Deduplication of all binder inside a module is changed by the deduplication of module binder before aggregating
• The current pass works in two step: Ast_typed -> list of locally defined decl -> Ast_aggregated. The new pass work in one step : Ast_typed to Ast_aggregated (and a preprocessing before). Therefore all functions are direct mappers.
• Expose function that doesn't take the local module as parameters.
• Separate the deduplication in an independent self-pass for redability.
• Homogenisation with the other pass

Side-effect : this change triggered a bug in the monomorphisation self-pass that is solved in the MR.