Support generation of strings >64k in length in Java
Support generation of strings >64k in length in Java

This was needed for a test case. Java has a built-in limit on
constant size and this works around the limit.

Change-Id: Id9ad0619a7eb5a76006babd1a22946e6015bd8f4

vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref