Add a query annotation to enable batching across multiple tables

[GeorgyBocharov]

What do you want to change?

Currently, sqlc only supports the :batchexec annotation, which allows for combining multiple inserts into the same table within a single batch. While this is useful, there are situations where you may need to insert data into multiple tables. In such cases, you might want sqlc to simply queue the queries in a batch and return them, enabling you to pass the same batch to another sqlc batch function. This way, you can execute the batch once all queries have been queued.

What database engines need to be changed?

PostgreSQL

What programming language backends need to be changed?

Go