fix: multicast group update

[juan-malbeclabs]

This pull request improves the CLI's handling of bandwidth values for the multicastgroup update command, ensuring that human-readable formats like "1Gbps" and "100Mbps" are correctly parsed. It also adds comprehensive tests to verify the new parsing logic.

CLI improvements

• The multicastgroup update command now properly parses human-readable bandwidth values (e.g., "1Gbps", "100Mbps") passed to the --max-bandwidth flag, making the CLI more user-friendly.
• The max_bandwidth argument in UpdateMulticastGroupCliCommand is now validated using the new validate_parse_bandwidth function, enabling correct parsing of various bandwidth formats.
• The CLI module imports the new validate_parse_bandwidth validator to support this enhanced parsing.

Testing enhancements

• Added a new test test_cli_multicastgroup_update_bandwidth_parsing to verify correct parsing of multiple bandwidth formats and to ensure invalid formats are rejected, improving reliability and maintainability.

Testing Verification

• Show evidence of testing the change