Provide raw mutateIn API

We allow users to use custom serialized objects and store them in Couchbase using RawJsonDocument, rather than having to converting to a JsonObject to then have to de-serialize it again to do the write.

Similarly, we allow users to access these raw bytes (for custom serialization) using the subdocument API using IncludeRaw() - https://docs.couchbase.com/sdk-api/couchbase-java-client/com/couchbase/client/java/subdoc/LookupInBuilder.html#includeRaw-boolean-.

It would be good to have some kind of equivalent raw-byte API for the mutation side of the subdocument API, so that users do not have to serialize then deserialize their objects again like so:

newsBucket.mutateIn("exampleDoc")

    .arrayAppend(

        "exampleField",

        JsonObject.fromJson(

            objectMapper.writeValueAsString(exampleObject)))