Optimize JDWP stack local values access

The StackFrame.GetValues and StackFrame.SetValues JDWP commands can refer to
multiple variables at the same time in a given frame. However we used to walk
the stack until getting to the requested frame for each variable.

Now, we walk the stack only once until getting to the frame so the context is
initialized. Then we read/write value for each variable from this context.

Bug: 17343501
Bug: 15680615
(cherry picked from commit 8009f39c)

Change-Id: I70f64b25e4b20860f5446b8c540345d5e71ec4a9