pkill command works unreliably (moved from save-cli)

[sanyavertolet]

Original issue: saveourtool/save-cli#338

[0x6675636b796f75676974687562]

• On JVM (Java 9+), you can use ProcessHandle.destroy
• Be sure to kill not only the process but also its children
• In K/N on UNIX, you can indeed run kill (not pkill -- that's too broad) with SIGTERM followed with SIGKILL after a time-out
• In K/N on Windows, you can rely on pskill.exe from SysInternals or taskkill.exe, available in modern Windows versions. .