It's not clear to me if dropping support for this functionality was intentional.

Chain of events:

- #21689 removed test coverage due to a misunderstanding due, I believe, to this functionality being generally supported by all platforms except macOS which does not and returns a different format
- #21756 removed support and caused this regression
- #21690 restores the test coverage that would have caught this regression

Currently, neither the test coverage before #21689 nor the coverage restored by #21690 pass since the merge of #21756.

BOOST_CHECK_EXCEPTION(s >> addr, std::ios_base::failure,
                          HasReason("BIP155 I2P address with length 3 (should be 32)"));
    BOOST_REQUIRE(!s.empty()); 
    s.clear();
    
    s << MakeSpan(ParseHex("06"                               
                           "10"                               
                           "fc000001000200030004000500060007" 
                           ));
    s >> addr;
    BOOST_CHECK(addr.IsValid());
    BOOST_CHECK(addr.IsCJDNS());
    BOOST_CHECK(!addr.IsAddrV1Compatible());
    BOOST_CHECK_EQUAL(addr.ToString(), "fc00:1:2:3:4:5:6:7");
    BOOST_REQUIRE(s.empty());
    
    s << MakeSpan(ParseHex("06"                               
                           "10"                               
                           "aa000001000200030004000500060007" 
                           ));
    s >> addr;
    BOOST_CHECK(addr.IsCJDNS());
    BOOST_CHECK(!addr.IsValid());
    BOOST_REQUIRE(s.empty());
    
    s << MakeSpan(ParseHex("06" 
                           "01" 
                           "00" 
                           ));
    BOOST_CHECK_EXCEPTION(s >> addr, std::ios_base::failure,