improve embeddings handling

[ChuckHend]

• changes default embedding location from new column on existing table to a new table
• updates the triggers so that they always take all inserts/updates as a batch rather than each row as a separate item. this is a huge performance improvement.
• realtime updates are only compatible with embeddings being on their own table (TableMethod::join). This improves efficiency for cases where realtime is beneficial by not rewriting the large tuples twice, and keeps the triggers more simple (if embeddings on same table, then the update of embeddings will trigger as well, causing an infinite loop).
• adds a view that joins embeddings to source table
• adds a migration to transition all existing realtime vectorize jobs from TableMethod::append to TableMethod::join, which moves their embeddings to their own table in the vectorize schema.