This PR makes all JS db packages to have uniform interface: `new
Database(...)` constructor with explicit `connect()` and `close()`
methods.
Also, this PR adds docstrings in the code and properly support few
better-sqlite options (readonly, fileMustExist, timeout)
Closes#3334
- now, most of the work is happening on the main thread
- for database in browser, we still have dedicated WebWorker - but it is used only for OPFS access and only for that
- for syn in browser we still offload sync operations to the WebWorker