Generate warnings if Pico STDIO init called (#1467)

Warn the user that the Pico SDK STDIO calls (stdio_init_all, stdio_usb_init,
stdio_uart_init) are not supported or needed at compile time.  See multiple
issues #1433 #1347 #1273 #1251 and others.

cores/rp2040/Arduino.h

@@ -129,3 +129,14 @@ constexpr uint32_t __bitset(const int (&a)[N], size_t i = 0U) {
     return i < N ? (1L << a[i]) | __bitset(a, i + 1) : 0;
 }
 #endif
+
+// Warn users trying to use Pico SDK's STDIO implementation
+#include <pico/stdio.h> // Ensure it won't be re-included elsewhere
+#undef stdio_uart_init
+#define stdio_uart_init(...) static_assert(0, "stdio_uart_init is not supported or needed. Either use Serial.printf() or set the debug port in the IDE to Serial/1/2 and use printf().  See https://github.com/earlephilhower/arduino-pico/issues/1433#issuecomment-1540354673 and https://github.com/earlephilhower/arduino-pico/issues/1433#issuecomment-1546783109")
+#undef stdio_init_all
+#define stdio_init_all(...)  static_assert(0, "stdio_init_all is not supported or needed. Either use Serial.printf() or set the debug port in the IDE to Serial/1/2 and use printf().  See https://github.com/earlephilhower/arduino-pico/issues/1433#issuecomment-1540354673 and https://github.com/earlephilhower/arduino-pico/issues/1433#issuecomment-1546783109")
+#undef stdio_usb_init
+#define stdio_usb_init(...)  static_assert(0, "stdio_usb_init is not supported or needed. Either use Serial.printf() or set the debug port in the IDE to Serial/1/2 and use printf().  See https://github.com/earlephilhower/arduino-pico/issues/1433#issuecomment-1540354673 and https://github.com/earlephilhower/arduino-pico/issues/1433#issuecomment-1546783109")
+
+