12278 add ipaddressfield serializer for OpenAPI spectacular typing

[arthanson]

Fixes: #12278

Creates a serializer for the IPAddressField so typing works correctly for OpenAPI eliminating warnings over the type (the default schema overrides weren't working for this). It's defined in nestedserializers due to scoping (serializers include nestedserializers).

[arthanson]

@jeremystretch this should be ready, moved IPAddressField serializer to separate file. I didn't find an auto field mapper for DRF, the closet I found was this discussion (encode/django-rest-framework#3244) but doesn't look like something we would want to do (monkey patching ModelSerializer) as "No, the recommended way is to just specify the field on the serializer class - not a big deal."

[jeremystretch]

I didn't find an auto field mapper for DRF

Ack. I must have been thinking about something else; probably django-filters. Apologies for the wild goose chase!