Output the @JsonTypeInfo information when serializing untyped attributes and collections

I encountered a problem when serializing untyped collections (e.g. `List<Object>`) containing objects from a class tree using `@JsonTypeInfo` and `@JsonTypeName` annotations: the additional property indicating the object's type is not serialized.

Jackson only outputs the type property for root objects or for collections and attributes typed with the base class (the one having the `@JsonTypeInfo`).

The problem can be traced back to `SerializerProvider` where `findValueSerializer` is called for untyped properties and collections whereas `findTypedValueSerializer` is called for typed ones.

I changed `SerializerProvider` so that `findValueSerializer` is always routed to `findTypedValueSerializer`. This solves the issue, but one test is failing:

```
Failed tests:   testMixedRefsIssue188(com.fasterxml.jackson.databind.struct.TestObjectId): null 
expected:<...er":null,"reports":[[2]},{"id":2,"name":"Second","manager":1,"reports":[]}]]}>
 but was:<...er":null,"reports":[[{"id":2,"name":"Second","manager":1,"reports":[]}]},2]]}>
```

Understanding this side effect is currently beyond my understanding of Jackson's internals. Is the proposed solution the right approach? Any idea on what causes the test to fail?