Dynamic groups should fail closed if filter is invalid

[glennmatthews]

Closes: #N/A but see also nautobot/nautobot-app-golden-config#626

What's Changed

• If a DynamicGroup has an invalid filter, its members() was failing open (all objects returned) instead of closed (no objects returned). This adds logic to call filterset.is_valid() and fail closed if the filterset is invalid.
• Enhance the audit_dynamic_groups command to call DynamicGroup.clean_filter() to also flag groups with invalid filter values.

>>> Auditing existing DynamicGroup data for invalid filters ...
    DynamicGroup "Bad Filter" has an invalid filter: {'platform': ['Enter a list of values.']}

>>> Please fix the broken filters stated above according to the documentation available at:
<nautobot-home>/static/docs/installation/upgrading-from-nautobot-v1.html#ui-graphql-and-rest-api-filter-changes

This is important for 2.0 as many existing DGs may have filters that become invalid as a result of the upgrade and should fail closed instead of failing open.

TODO

• Explanation of Change(s)
• Added change log fragment(s) (for more information see the documentation)
• Attached Screenshots, Payload Example
• Unit, Integration Tests
• n/a Documentation Updates (when adding/changing features)
• n/a Example Plugin Updates (when adding/changing features)
• Outline Remaining Work, Constraints from Design