[addon-operator] use shell-operator as a lib

[fuldaxxx]

Overview

This PR updates addon-operator integration with shell-operator to the new library-oriented flow and removes reliance on shell-operator app globals for debug socket wiring.

What this PR does / why we need it

• bumps github.com/flant/shell-operator;
• switches engine creation to shell_operator.NewBareShellOperator(...) with explicit options;
• keeps shell-operator debug commands (queue/config/hook/raw) aligned with addon-operator socket by setting debug.DefaultSocketPath = cfg.Debug.UnixSocket (both in main.go and
  NewAddonOperator);
• keeps config projection via ShellOperatorConfig(...) for AssembleCommonOperatorFromConfig(...);
• updates shutdown path to context-based graceful shutdown with timeout and error logging;
• refreshes tests to validate new debug socket contract via debug.DefaultSocketPath