* fix(cli): close every browser on SIGTERM and SIGINT through one launch owner
* fix(cli): own SIGTERM before the GPU probe browser launches
* fix(cli): keep tests on the managed GPU mode and drop the engine signal flag
* test(cli): give the browser fallback fake a process handle
* test(cli): signal the GPU probe case only once the signal owner is installed
* test(cli): mark the launching case only after the signal owner is installed