[C++] Enable the creation of named table relations

We think that the `Named Table` relation supported by substrait is an important abstraction in HPC to enable remote executions. To enable the creation of named tables with the `engine::SerializePlan` API, we would like to add the support of `InMemoryDataset` to scan nodes to be used to convert to substrait plans. The idea is to save the `names` of a named table in the metadata of the schema used to create the InMemoryDataset.