Typed crud values

[simolus3]

Most of our SDKs (I've checked Dart and JS) represent CrudEntry.opData and CrudEntry.previousValues as a Map<String, Any?>. In Kotlin however, we're using a Map<String, String?> (reported on Discord). This is somewhat unfortunate, as:

1. It means that the Supabase connector will upload everything as a string, regardless of the actual type. While this isn't a huge problem since Postgrest will cast, it's also not great.
2. It's a blocker if we want to represent binary data in the future.
3. Since SQLite is dynamically typed, it would be nice to properly preserve type information so that users can act on the type of values at runtime.

This PR adds information to construct the type of values in opData and previousValues with backwards-compatibility in mind:

1. As a technically-breaking change, the CrudEntry constructor is made internal. Users probably weren't invoking it directly though, that's an SDK responsibility.
2. To keep the public Map<String, String?> type, this introduces the SqliteRow interface extending that type, while also providing a getter to get access to typed values.
3. The interface also has a method to return a JsonObject, which we can use in the Supabase connector to upload values unchanged (giving users a serializable object without making SqliteRow serializable, which would blow up the framework size).

This way, existing reads on the fields still work because we have a Map<String, String?> type.

[stevensJourney]

Happy with the changes here. This looks like a good solution which greatly improves the DX while maintaining backwards compatibility.