Enhance "Jsonb" to allow "fromJson" to handle "JsonStructure" as input

Hey there,

It would be nice to enhance the interface [javax.json.bind.Jsonb](https://github.com/eclipse-ee4j/jsonb-api/blob/master/api/src/main/java/javax/json/bind/Jsonb.java) to allow handling of [javax.json.JsonStructure](https://github.com/eclipse-ee4j/jsonp/blob/master/api/src/main/java/javax/json/JsonStructure.java) as input for deserialization (unmarshalling to a Java class).

This means, there should be two new methods :
```java
public interface Jsonb extends AutoCloseable {
...
T fromJson(JsonStructure jsonStruct, Class type) throws JsonbException;
T fromJson(JsonStructure jsonStruct, Type runtimeType) throws JsonbException;
}
```
Yasson already supports this for the opposite direction (serialization):
```java
JsonObject jsonObj = Json.createObjectBuilder().add("name", "Peter Parker").add("age", 18).build();
Jsonb jsonb = JsonbBuilder.create();
System.out.println(jsonb.toJson(jsonObj));
// Prints {"name":"Peter Parker","age":18}
```
But currently JSON-B does not support deserialization like:
```java
Person person = jsonb.fromJson(jsonObj, Person.class);
```
Unfortunately this is a breaking change, but it could be implemented in the interface with a default method that throws an "UnsupportedOperationException" in case the provider does not implement it.

What do you think?

Cheers,
Michael

Start with api/src/main/java/javax/json/bind/Jsonb.java and review the existing fromJson overloads and the compatibility concerns raised in the issue. Confirm how JsonStructure input should be deserialized and whether provider behavior needs corresponding API coverage; done means the proposed overloads are defined with the requested signatures and their expected behavior is verified.

Written by the indexing model from the issue text.