[KW-search] Google Drive: Standardize parents and internal ID

[philipperolet]

Goal is to ensure for Google Drive that:

• Parent ids used in the parents[] array in core data_source_nodes and internal ids from connectors should now match node_id in core data_sources_nodes (= document_id for docs, table_id for tables, folder_id for folders);
• the convention that parents[0] = node_id should be enforced.

The connector should be thoroughly inspected. If there is a convention mismatch, fix it; explained in details in #9069

As noted here : https://github.com/dust-tt/dust/pull/9261/files#r1879852550 , we should add parent_id parameter in upserts as part of this card once parents are standardized.

[philipperolet]

we'll need to migrate folders too here since they're already written on

[tdraier]

Found a lot of inconsistencies in existing parents array, may need to be fixed first : #9250

[philipperolet]

As per IRL, #9250 and #9256 will be handled at the same time, using the common migration script of #9277