Move search app out of renderer into shared process or extension host

[bpasero]

We need to remove node dependencies of the renderer for our sandbox effort. Search is currently a process that is triggered from the renderer (via vs/workbench/services/search/electron-browser/searchService et al). Going forward, we should move this into one of the processes that is allowed to execute node:

• shared process
• extension host

Filing this to get a discussion starting how to tackle this. With terminals moved, @Tyriar and @meganrogge have demonstrated that the shared process is a viable host for native processes and the patterns used for terminals can be applied to this one as well.

#116337 has a diagram for how the shared process today is being used as host for privileged processes.

[roblourens]

It has been the plan for awhile to move this to the EH. I can't find the old discussion about the architecture and the possible perf issues of running search in the EH, but I think this has been proved in Remote, and we can revisit this. @jrieken @kieferrm

[bpasero]

Would be great if we can push this to stable for the September release given it is now enabled in insiders.

[bpasero]

I verified the search.forceSearchProcess setting. It needs a restart and we do not tell the user, but my understanding is this setting goes away in October anyway.