Theia: run embedded slapos in a service + bash completions + upate to 1.8.0

Use https://lab.nexedi.com/nexedi/slapos.core/merge_requests/265 to run slapos in a controlled services.

Enable bash-completions so that we can benefit from existing completions and generate fish completions using https://lab.nexedi.com/nexedi/slapos.core/merge_requests/253

Apply a workaround for segmentation faults when exiting theia-open

Update to 1.8.0 https://github.com/eclipse-theia/theia/blob/v1.8.0/CHANGELOG.md#v180---26112020