[BridgeJS] @JSClass does not work on `public` or `package` types

The macro adds a conformance to `_JSBridgedClass`, but generates initializer and jsObject field with internal access level.

```
Property 'jsObject' must be declared public because it matches a requirement in public protocol '_JSBridgedClass'
Initializer 'init(unsafelyWrapping:)' must be declared public because it matches a requirement in public protocol '_JSBridgedClass'
```