manifest: Add arduino-core build snippet

[soburi]

Added an arduino-core Zephyr snippet that applies the common ArduinoCore config.
This snippet able to eliminate special handling *.overlay and *.conf.

[Copilot]

Pull request overview

This PR introduces a Zephyr build snippet (arduino-core) for the ArduinoCore-zephyr module so board-specific ArduinoCore configuration (Kconfig fragments and devicetree overlays) can be applied via west build -S arduino-core, removing per-sample CMake special-casing.

Changes:

• Add a new arduino-core snippet (YAML + README + common .conf) and register snippet_root in zephyr/module.yml.
• Remove sample-level CMake logic that auto-discovers variant overlay files; update sample READMEs and CI to build using -S arduino-core.
• Add (currently header-only) per-board variant .conf files referenced by the snippet.

Reviewed changes

Copilot reviewed 34 out of 34 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
zephyr/snippets/arduino-core/snippet.yml	Defines the arduino-core snippet and board-specific .conf/.overlay appends.
zephyr/snippets/arduino-core/README.rst	Documents how to use the snippet via west build -S arduino-core.
zephyr/snippets/arduino-core/arduino-core.conf	Common snippet Kconfig enabling CONFIG_ARDUINO_API.
zephyr/module.yml	Registers snippet_root: zephyr so Zephyr can discover module-provided snippets.
variants/rpi_pico/rpi_pico.conf	Adds variant Kconfig file referenced by the snippet.
variants/nrf9160dk_nrf9160/nrf9160dk_nrf9160.conf	Adds variant Kconfig file referenced by the snippet.
variants/nrf52840dk_nrf52840/nrf52840dk_nrf52840.conf	Adds variant Kconfig file referenced by the snippet.
variants/native_sim/native_sim.conf	Adds variant Kconfig file referenced by the snippet.
variants/cc3220sf_launchxl/cc3220sf_launchxl.conf	Adds variant Kconfig file referenced by the snippet.
variants/beagleconnect_freedom/beagleconnect_freedom.conf	Adds variant Kconfig file referenced by the snippet.
variants/arduino_nano_33_iot/arduino_nano_33_iot.conf	Adds variant Kconfig file referenced by the snippet.
variants/arduino_nano_33_ble/arduino_nano_33_ble.conf	Adds variant Kconfig file referenced by the snippet.
variants/arduino_nano_33_ble_nrf52840_sense/arduino_nano_33_ble_nrf52840_sense.conf	Adds variant Kconfig file referenced by the snippet.
variants/arduino_mkrzero/arduino_mkrzero.conf	Adds variant Kconfig file referenced by the snippet.
samples/threads_arduino/README.rst	Updates build docs to use the snippet.
samples/threads_arduino/CMakeLists.txt	Removes overlay auto-discovery logic now handled by the snippet.
samples/spi_controller/CMakeLists.txt	Removes overlay auto-discovery logic now handled by the snippet.
samples/serial_event/README.rst	Updates build command to use the snippet (and fixes sample path).
samples/serial_event/CMakeLists.txt	Removes overlay auto-discovery logic now handled by the snippet.
samples/i2cdemo/README.rst	Updates build docs to use the snippet.
samples/i2cdemo/CMakeLists.txt	Removes overlay auto-discovery logic now handled by the snippet.
samples/hello_arduino/README.rst	Updates build docs to include the snippet.
samples/hello_arduino/CMakeLists.txt	Removes overlay auto-discovery logic now handled by the snippet.
samples/fade/README.rst	Updates build docs to use the snippet (removes extra-module flag).
samples/fade/CMakeLists.txt	Removes overlay auto-discovery logic now handled by the snippet.
samples/button_press_led/README.rst	Updates build docs to use the snippet (removes extra-module flag).
samples/button_press_led/CMakeLists.txt	Removes overlay auto-discovery logic now handled by the snippet.
samples/blinky_arduino/README.rst	Updates build docs to use the snippet (removes extra-module flag).
samples/blinky_arduino/CMakeLists.txt	Removes overlay auto-discovery logic now handled by the snippet.
samples/attach_interrupt/README.rst	Updates build docs to use the snippet (removes extra-module flag).
samples/attach_interrupt/CMakeLists.txt	Removes overlay auto-discovery logic now handled by the snippet.
samples/analog_input/README.rst	Updates build docs to use the snippet (and fixes sample path).
samples/analog_input/CMakeLists.txt	Removes overlay auto-discovery logic now handled by the snippet.
.github/workflows/build.yml	Updates CI builds to pass -S arduino-core.

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