feat: add "toString" function to IPAddress (#2306)

Signed-off-by: Virens <[email protected]>

Author: VirensCn

Diff for: cores/arduino/IPAddress.cpp

@@ -107,3 +107,9 @@ size_t IPAddress::printTo(Print &p) const
   return n;
 }
 
+String IPAddress::toString() const
+{
+  char szRet[16];
+  sprintf(szRet, "%u.%u.%u.%u", _address.bytes[0], _address.bytes[1], _address.bytes[2], _address.bytes[3]);
+  return String(szRet);
+}

Diff for: cores/arduino/IPAddress.h

@@ -82,6 +82,7 @@ class IPAddress : public Printable {
     IPAddress &operator=(uint32_t address);
 
     virtual size_t printTo(Print &p) const;
+    String toString() const;
 
     friend class EthernetClass;
     friend class UDP;