Support for record types

Since Dart 3 we have had [records](https://dart.dev/language/records). They're great and I use them extensively. I just ran into a problem though - Hive doesn't seem to support them yet, and whenever trying to save objects that include them, you get an error like this:

`HiveError (HiveError: Cannot write, unknown type: (int, int). Did you forget to register an adapter?)`

It's also **not** possible to generate type adapters like this:
```dart
@HiveType(typeId: 3)
typedef IntVec = (int, int);
```

(although this solution would not be great anyway)

Reproduce the Dart 3 records case described in the issue, including the `(int, int)` value and the shown `@HiveType` typedef. Then trace Hive's handling of unknown types and adapter generation; done means objects containing records can be saved without the reported HiveError.

Written by the indexing model from the issue text.