Add IPv6 support and sfDns

- Grow sfIpAddress to hold IPv6 addresses and add address types

- Make sfIpAddress_fromString not resolve network names anymore, matching sf::IpAddress::fromString, and add the deprecated sfIpAddress_resolve

- Add sfDns for resolving hostnames and querying NS, MX, SRV and TXT records

test/Network/Dns.test.cpp

@@ -0,0 +1,25 @@
+#include <CSFML/Network/Dns.h>
+#include <CSFML/System/Alloc.h>
+
+#include <catch2/catch_test_macros.hpp>
+
+#include <cstring>
+
+TEST_CASE("[Network] sfDns")
+{
+    SECTION("sfDns_resolve")
+    {
+        size_t       count     = 0;
+        sfIpAddress* addresses = sfDns_resolve("127.0.0.1", nullptr, 0, sfSeconds(1), &count);
+        REQUIRE(addresses != nullptr);
+        REQUIRE(count == 1);
+        CHECK(std::strcmp(addresses[0].address, "127.0.0.1") == 0);
+        sfFree(addresses);
+
+        addresses = sfDns_resolve("::1", nullptr, 0, sfSeconds(1), &count);
+        REQUIRE(addresses != nullptr);
+        REQUIRE(count == 1);
+        CHECK(std::strcmp(addresses[0].address, "::1") == 0);
+        sfFree(addresses);
+    }
+}