Backport restart-watcher script to 2.26.x for 1.8.0 release
Backport the restart-watcher to the old version and release.
Some hard-to-debug error occurs in WPE WebKit 2.28.1 while the mirr.OS display app is running, crashing the renderer process. While WPE is stuck at 2.28.1 in Ubuntu Focal repositories (see https://answers.launchpad.net/ubuntu/+source/wpewebkit/+question/692844) and the newly added sched_setattr
permission in process-control
doesn't seem to remedy the dysfunctional --restart-on-webprocess-failure
flag.