Mass Order using builder

Here is the MassOrder example I was thinking of.  It quite nicely encapsulates all of the ObjectLayout complexity within the builder (with the exception of `extends StructuredArray<>` on the `MassOrderWithBuilder` class).

One other interesting case is the `String instructionId` in our real system this is actually a fixed length value (24 bytes).  I'm wondering if there would be a way to inline that allocation too?