Add stack size check methods to WhiteBox API

VM JSR292 tests generate method handle call graphs which use a lot of stack. On embedded machines the stack size is limited, so we often get StackOverflowError. On the big machines we still want to generate big method handle graphs. The best solution to this seems to check remaining stack size on-the-fly in the tests. Since there is no way to query remaining stack size from VM, we propose adding such methods to WhiteBox API.

A diff with suggested changes is attached