Fix IPv6-only builds where platform LwIP has IPv4 (#10879)

#### Problem

When LwIP is configured for IPv6 only, its type `ip_addr_t` is identical
to `ip6_addr_t`; otherwise they are different. PR #10791 made the
incorrect assumption that we would never build CHIP without IPv4 when
then platform LwIP is configured with IPv4, and left out the constructor
overload necessary for that case.

#### Change overview

Enable the `ip_addr_t` constructor if `LWIP_IPV4` is true.

#### Testing

Built
```
scripts/build/build_examples.py \
    --target esp32-m5stack-all-clusters-ipv6only build`
```

Author: kpschoedel

src/inet/IPAddress.cpp

@@ -76,7 +76,7 @@ IPAddress::IPAddress(const ip6_addr_t & ipv6Addr)
     memcpy(Addr, &ipv6Addr, sizeof(ipv6Addr));
 }
 
-#if INET_CONFIG_ENABLE_IPV4
+#if INET_CONFIG_ENABLE_IPV4 || LWIP_IPV4
 
 IPAddress::IPAddress(const ip4_addr_t & ipv4Addr)
 {
@@ -106,6 +106,10 @@ IPAddress::IPAddress(const ip_addr_t & addr)
     }
 }
 
+#endif // INET_CONFIG_ENABLE_IPV4 || LWIP_IPV4
+
+#if INET_CONFIG_ENABLE_IPV4
+
 ip4_addr_t IPAddress::ToIPv4() const
 {
     ip4_addr_t ipAddr;

src/inet/IPAddress.h

@@ -147,7 +147,7 @@ class DLL_EXPORT IPAddress
 
 #if CHIP_SYSTEM_CONFIG_USE_LWIP
     explicit IPAddress(const ip6_addr_t & ipv6Addr);
-#if INET_CONFIG_ENABLE_IPV4
+#if INET_CONFIG_ENABLE_IPV4 || LWIP_IPV4
     explicit IPAddress(const ip4_addr_t & ipv4Addr);
     explicit IPAddress(const ip_addr_t & addr);
 #endif // INET_CONFIG_ENABLE_IPV4