Allow multiple MATCH statements within a single query

[Dtenwolde]

There can only be one MATCH statement in a single query. It should be possible to have multiple MATCH statements, of which the results can be joined using the cross-product. This would be similar to a subquery

https://github.com/cwida/duckpgq-experiments/issues/27

[Dtenwolde]

Right now we save the result of the TransformMatchNode in parse_data, which can only store one node. However, a query can contain more than 1, in which case this method fails. A suggestion was made to not store the data in parse_data, but serialize the node and add it as a BLOB argument to the node in the logical query plan (something along these lines). Then we later deserialize the node whenever we reach it.