Support COPY TO statement

[rfdavid]

Proposal

This feature will enable users to export query results to either CSV or PARQUET files using our current COPY command. In the same way, we already perform COPY FROM, the idea is to use the same statement using COPY TO, similar to DuckDB Copy.

Examples

Add HEADER and DELIMITER properties
COPY Person TO "person.csv" (HEADER=true, DELIM='|');

Write a specific query result to result.parquet
COPY (MATCH (a:person) RETURN a.name) TO "result.parquet"

TODO

The idea is to break down the deliverable of the complete feature in the following order:

1. Implement COPY ([query]) TO "file.csv"
2. Support .parquet file type
3. Optimize via parallel processing