Release GroupingNamespace when module/submodule is done

We currently do not wipe GroupingNamespace because it is used after inference by UsesStatementSupport.getSourceGrouping().

Logic in UsesStatementSupport needs to be updated to store a StmtContext.replicaAsChildOf() for its context and add it to a dedicated namespace in that statement. During UsesStatementSupport.createEffective() we need to pick this replica up and use it as the source of the effective statement.

This way we do not look into GroupingNamespace after inference, have the grouping tied down with a proper reference, which will be cleared when we build the statement.

Once this is done, add GroupingNamespace to RootStatementContext.SWEPT_NAMESPACES.