This CL adds further support to the test wrapper. We are now able to
run almost all mjsunit/debug-step-* tests using the inspector backend.
debug-stepframe-* tests are not yet supported since inspector does not
know a 'frame' step type.
The interface has also been improved to be able to move these tests to
inspector mostly without modification.
BUG=v8:5330
Review-Url: https://codereview.chromium.org/2466273005
Cr-Commit-Position: refs/heads/master@{#40800}
