Register processes to be killed when extension is unloaded

[DonJayamanne]

Processes spawned need to be killed in the dispose handler.
I.e. when extension is unloaded/deactivated we need to shutdown all processes started by the extension.

• Kill debugger processes spawned
• Kill linter, formatter, jedi processes spawned

[koliyo]

I experienced the same problem in #4221

After reloading the window the processes are no longer in the VS Code Process Explorer, but they are still running on the OS until I kill them of manually.

Mac OS Mojave

[koliyo]

Note, if you start child processes with posix pgid attributes you can kill of child processes automatically when killing the parent process.

Here is some go-code I am using:

// NOTE: This code does not work for windows, therefore separate compile units

// StartProcess _
func StartProcess(cmd *exec.Cmd) error {
	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
	return cmd.Start()
}

// KillProcess _
func KillProcess(cmd *exec.Cmd) error {
	// job.Cmd.Process.Kill()
	return syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
}

This approach is taken from https://medium.com/@felixge/killing-a-child-process-and-all-of-its-children-in-go-54079af94773

[DonJayamanne]

Solution:

• Modify ProcessService to implement IDisposable
• In dispose method kill the process (if not already dead)
• Registry this process class in the disposable registry (either via ctor or where it gets instantiated in https://github.com/Microsoft/vscode-python/blob/5507f5d8226f12005db524a04c181b64ec7fe658/src/client/debugger/debugAdapter/Common/processServiceFactory.ts)

[DonJayamanne]

This needs to be completed before the Azdo Timeouts are addressed.