[PING] Update SendBuffer fill method (#7782)

The ping utility found in various versions of Windows fills the optional
data field in the ICMP echo request structure with ASCII characters from
'a' to 'w' wrapping back around until SendBuffer is full.

Future TO-DO: Compare ReplyBuffer data to SendBuffer.

base/applications/network/ping/ping.c

···
             exit(1);
         }
 
-        ZeroMemory(SendBuffer, RequestSize);
+        /* Windows ping utility fills the optional data field with
+         * ASCII characters from 'a' to 'w', wrapping back around
+         * until SendBuffer is full. */
+        for (ULONG i = 0; i < RequestSize; i++)
+            ((PUCHAR)SendBuffer)[i] = (UCHAR)('a' + (i % ('w' - 'a' + 1)));
     }
 
     if (Family == AF_INET6)
···
                                ReplyBuffer, ReplySize, Timeout);
     }
 
+    /* TODO: Compare ReplyBuffer data to SendBuffer. */
     free(SendBuffer);
 
     if (Status == 0)