Fix: good format when using diagVM

[1yam]

This pull request introduces improvements to the way IPv6 status is fetched and handled for nodes, ensuring compatibility with different node versions and providing a fallback mechanism. The main enhancement is the introduction of version-aware logic for selecting the appropriate IPv6 check endpoint, which increases reliability across nodes running different software versions.

Key changes:

IPv6 Fetching Logic

• Added fetch_ipv6_from_diag and get_ipv6_fetch_method methods to select the correct IPv6 fetch method based on the node's cached version, defaulting to a diagnostic endpoint for older or unrecognized versions.
• Updated the code to use the new get_ipv6_fetch_method when scheduling IPv6 checks for all nodes, ensuring the correct endpoint is used dynamically.

Endpoint Constants

• Introduced new constants CRN_PATH_IPv6_CHECK and DIAG_VM_PATH_IPv6_CHECK to clearly distinguish between the standard and diagnostic IPv6 check endpoints.

Error Handling and Defaults

• Improved handling in the API response to ensure that if IPv6 check data is missing, a default CheckIPv6(host=False, vm=False) object is returned, preventing null values in the output.

Dependency

• Added the packaging library import to support version parsing for the new version-aware logic.