StackCounter handling of invoke instructions should add slots for invoke instruction at once instead of in 2 batches: if in a method like
int work() { return anotherInstanceMethod(); }
The stack will be 2 currently due to this buggy logic first adding another stack, making max 2, then decrementing back to 1 and to 0.

We need to ensure all calls to addStackInSlot should be atomic.

Courtesy to [~winterhalter] for test cases discovering this issue.