Fix perf-tool (somewhat)
The current scripting module makes heavy use of pre-standardized iterator/generator/promise APIs, at least for some of those support was pulled in SpiderMonkey 58.
Port to the new standardized replacements to get the module back into a working state.
Unfortunately this is all still very x-centric. I've added a --nested option locally which works to some extent, but windows still pop up on the "host".
No luck at all with wayland so far ...