Minor cleanup of RP2040 code post addition of Pico-PIO_USB

* Removed some compiler warnings, and cleaned out unnecessary warning suppression from CMake suppress_tinyusb_warnings()
* Made explicit family_configure_dual_usb_example() for DUAL mode examples as family_configure_target() may not generally be called multiple times for the same target

* Renamed library pico_pio_usb to tinyusb_picio_pio_usb to be clearer and avoid conflict if someone already has a pico_pio_usb in their project
* Added family_add_pico_pio_usb() method for adding Pico-PIO_SUB support to an existing example
* Allowed tinyusb_pico_pio_usb to be added to regular apps using the Pico SDK

hw/bsp/rp2040/family.c

@@ -127,8 +127,10 @@ void board_init(void)
 #ifndef BUTTON_BOOTSEL
 #endif
 
+#if CFG_TUH_RPI_PIO_USB || CFG_TUD_RPI_PIO_USB
   // Set the system clock to a multiple of 120mhz for bitbanging USB with pico-usb
   set_sys_clock_khz(120000, true);
+#endif
 
 #if defined(UART_DEV) && defined(LIB_PICO_STDIO_UART)
   bi_decl(bi_2pins_with_func(UART_TX_PIN, UART_TX_PIN, GPIO_FUNC_UART));