Sqlite: custom functions and aggretors

[robinheghan]

We should make it possible to define custom SQL functions and aggregators by exposing a Gren interface to the Node.js sqlite.function and sqlite.aggretor APIs.

https://nodejs.org/docs/latest-v22.x/api/sqlite.html#databasefunctionname-options-function
https://nodejs.org/docs/latest-v22.x/api/sqlite.html#databaseaggregatename-options