fix containers cleanup bug

[dmytrotkk]

This pull request introduces a new utility function, rm_legacy_containers, to help clean up legacy Docker containers with names starting with skale_. The function is integrated into several node operation workflows to ensure legacy containers are consistently removed during update and shutdown processes. Comprehensive tests for this new functionality have also been added.

Docker container cleanup improvements:

• Added a new function rm_legacy_containers in docker_utils.py to remove all containers with names starting with skale_ using Docker's filtering capabilities.
• Integrated calls to rm_legacy_containers into the update and shutdown flows for both base and fair node operations (base.py and fair.py), ensuring legacy containers are removed during these processes. [1] [2] [3] [4] [5]

Testing enhancements:

• Added rm_legacy_containers to the import lists in both the main code and test files. [1] [2] [3]
• Implemented a new test, test_rm_legacy_containers, to verify that containers with names starting with skale_ are properly removed.
• Added a real Docker test, test_get_all_skaled_containers_real, to ensure container name filtering works as expected.