Some embedders, like Electron, choose to start Node.js with
`only_terminate_in_safe_scope` set to `true`. In those cases, parts
of the API that expect execution termination to happen need to
be marked as able to receive those events. In our case, this is
the Ctrl+C support of the `vm` module (and Workers, but since
we’re in control of creating the `Isolate` for them, that’s a
non-concern there).

Add those scopes and add a regression test.