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

examples/dual/CMakeLists.txt

@@ -0,0 +1,12 @@
+cmake_minimum_required(VERSION 3.5)
+
+include(${CMAKE_CURRENT_SOURCE_DIR}/../../hw/bsp/family_support.cmake)
+
+project(tinyusb_dual_examples)
+family_initialize_project(tinyusb_dual_examples ${CMAKE_CURRENT_LIST_DIR})
+if (FAMILY STREQUAL "rp2040" AND NOT TARGET tinyusb_pico_pio_usb)
+    message("Skipping dual host/device mode examples as Pico-PIO-USB is not available")
+else()
+    # family_add_subdirectory will filter what to actually add based on selected FAMILY
+    family_add_subdirectory(host_hid_to_device_cdc)
+endif()