windows: set job object for executor and children

On Windows, if the `raw_exec` driver's executor exits, the child processes are
not also killed. Create a Windows "job object" (not to be confused with a Nomad
job) and add the executor to it. Child processes of the executor will inherit
the job automatically. When the handle to the job object is freed (on executor
exit), the job itself is destroyed and this causes all processes in that job to
exit.

Fixes: #23668
Ref: https://learn.microsoft.com/en-us/windows/win32/procthread/job-objects

.changelog/24214.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+windows: Fixed a bug where a crashed executor would orphan task processes
+```

drivers/shared/executor/executor_windows.go

@@ -9,17 +9,48 @@ import (
 	"fmt"
 	"os"
 	"syscall"
+	"unsafe"
 
 	"golang.org/x/sys/windows"
 )
 
-// configure new process group for child process
+// configure new process group for child process and creates a JobObject for the
+// executor. Children of the executor will be created in the same JobObject
+// Ref: https://learn.microsoft.com/en-us/windows/win32/procthread/job-objects
 func (e *UniversalExecutor) setNewProcessGroup() error {
 	// We need to check that as build flags includes windows for this file
 	if e.childCmd.SysProcAttr == nil {
 		e.childCmd.SysProcAttr = &syscall.SysProcAttr{}
 	}
 	e.childCmd.SysProcAttr.CreationFlags = syscall.CREATE_NEW_PROCESS_GROUP
+
+	// note: we don't call CloseHandle on this job handle because we need to
+	// hold onto it until the executor exits
+	job, err := windows.CreateJobObject(nil, nil)
+	if err != nil {
+		return fmt.Errorf("could not create Windows job object for executor: %w", err)
+	}
+
+	info := windows.JOBOBJECT_EXTENDED_LIMIT_INFORMATION{
+		BasicLimitInformation: windows.JOBOBJECT_BASIC_LIMIT_INFORMATION{
+			LimitFlags: windows.JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE,
+		},
+	}
+	_, err = windows.SetInformationJobObject(
+		job,
+		windows.JobObjectExtendedLimitInformation,
+		uintptr(unsafe.Pointer(&info)),
+		uint32(unsafe.Sizeof(info)))
+	if err != nil {
+		return fmt.Errorf("could not configure Windows job object for executor: %w", err)
+	}
+
+	handle := windows.CurrentProcess()
+	err = windows.AssignProcessToJobObject(job, handle)
+	if err != nil {
+		return fmt.Errorf("could not assign executor to Windows job object: %w", err)
+	}
+
 	return nil
 }