Support for Protobuf WellKnownTypes when generating schema with ProtobufMapper

Assuming we have a Java POJO such as:
```java
public record Test(String value, Instant ts) {
}
```

And then we use:
```scala
private val protobufMapper = ProtobufMapper.builder
.addModule(new JavaTimeModule)
.build()

val jacksonProtoSchema = protobufMapper.generateSchemaFor(classOf[Test])
```

The `ts` field will be automatically mapped as `double`. I'm looking at a way to have it converted to a Message type of `google.protobuf.Timestamp`. I've tried using a new module with custom ser/deserializers but the issue there is it drops `google.protobuf.` qualifiers for the type, using the simple name of the raw class instead.

I've looked at the code as well and cannot find anything that would support this so I'm not sure if I'm missing something or if this would be new functionality.