Add Room integration

[simolus3]

This adds a Room integration package for PowerSync.

This works by making the PowerSync SDK run queries against the connection pool managed for Room databases, which ensures that we have no conflict due to multiple write connections. One unfortunate downside is that the driver APIs exposed by Room are async-only. Using runBlocking to turn them synchronous is inefficient, but also blocked by Room (if we request a connection from a pool, we can only use it from a single coroutine). It looks like we may be able to use something like this as a workaround though. This PR works around that by introducing asynchronous transaction callbacks, but that will require more work to finalize.

This uses the new update hooks implemented in the core extension to query for updates after each transaction from the PowerSync SDK, these updates are automatically forwarded to Room (so a sync from PowerSync automatically updates Flows in Room).
Because we can't install a general update listener on Room databases, the other direction is more complicated. The best approach I could come up with here is to create a Room flow listening on all tables explicitly, and then call powersync_update_hook('get') to forward these writes to PowerSync.