Revert "feat(tools): add exec tool enhancement with background execution and …"

This reverts commit f901af8cbc.

pkg/tools/session_process_unix.go

@@ -1,14 +0,0 @@
-//go:build !windows
-
-package tools
-
-import (
-	"syscall"
-)
-
-func killProcessGroup(pid int) error {
-	if err := syscall.Kill(-pid, syscall.SIGKILL); err != nil {
-		_ = syscall.Kill(pid, syscall.SIGKILL)
-	}
-	return nil
-}