Changes in JSON.dump behaviour with cyclical structures

Ruby JSON appears to have changed parsing of errors between v2.6 and v2.7 (and JSON v2.2.0 vs v2.3.0). For example - when running:

```ruby
require 'json'

data = {}
data['cycle'] = data
JSON.dump(data)
```

**With Ruby v2.6.5 / JSON v2.2.0**

This raises a `SystemStackError`

**With Ruby v2.7.0 / JSON v2.3.0**

This causes `fatal (machine stack overflow in critical region)`
