Decoding an unsigned numeric value containing an exponent

#2227 added support for decoding numeric values containing an exponent, but it doesn't work for unsigned types:

```kotlin
Json.decodeFromString<Int>("1E2") // 100
Json.decodeFromString<UInt>("1E2") // JsonDecodingException
```

This is a request to add support for decoding unsigned types from numeric values ​​that contain an exponent.