Add @IPv6Ignore and @IPv6Only annotations for unit tests

Our CI executes unit tests both with and without having "-Dtest.ipv6=true". (The specified value is passed to the system property "java.net.preferIPv6Addresses".).
In some cases, we need to write unit tests that work only on IPv4 or only on IPv6. For example, unit tests for IPAddressAccessControlHandler.
I would like to propose to add @IPv6Ignore and @IPv6Only annotation (like @ProxyIgnore annotation for unit tests which are not suitable to test with proxy).