Merge #21037: fuzz: Avoid designated initialization (C++20) in fuzz tests

dee2d6f fuzz: Avoid designated initialization (C++20) in fuzz tests (practicalswift)

Pull request description:

  Avoid designated initialization (C++20) in fuzz tests.

  Context: bitcoin/bitcoin#20197 (comment), bitcoin/bitcoin#20936 (comment)

ACKs for top commit:
  MarcoFalke:
    cr ACK dee2d6f
  dhruv:
    code review ACK dee2d6f
  ajtowns:
    utACK dee2d6f

Tree-SHA512: 5940fab6e97a2b11dd3b1475d2cffa2840dc2e6ec34bd9f9df90f948709cab98fd1c513d5dd104816d33a525a6e9710b8715b02db941e35d84f92bc211f56d1d

Author: MarcoFalke

src/test/fuzz/util.h

@@ -269,8 +269,8 @@ inline CNetAddr ConsumeNetAddr(FuzzedDataProvider& fuzzed_data_provider) noexcep
     const Network network = fuzzed_data_provider.PickValueInArray({Network::NET_IPV4, Network::NET_IPV6, Network::NET_INTERNAL, Network::NET_ONION});
     CNetAddr net_addr;
     if (network == Network::NET_IPV4) {
-        const in_addr v4_addr = {
-            .s_addr = fuzzed_data_provider.ConsumeIntegral<uint32_t>()};
+        in_addr v4_addr = {};
+        v4_addr.s_addr = fuzzed_data_provider.ConsumeIntegral<uint32_t>();
         net_addr = CNetAddr{v4_addr};
     } else if (network == Network::NET_IPV6) {
         if (fuzzed_data_provider.remaining_bytes() >= 16) {