Removed GetDefaultIsolate{Debugger,ForLocking,StackGuard}.

Some first steps towards removing the default Isolate. Fixed argument
order on the way, incl. temporary helpers.

BUG=359977
LOG=y
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/238803002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20747 ce2b1a6d-e550-0410-aec6-3dcde31c8c00