core: Add peripheral reinit for pinmux switching

[soburi]

Allows Arduino APIs to switch a pin between GPIO and peripheral functions by re-running the selected device init path when the requested owner changes.

This is an interim pinmux handoff mechanism for boards where sketches may move a pin back and forth between serial/GPIO/PWM-style use.

In practice, this code is temporary fix.
Here, for merge management purposes, it's made identical to Arduino, but
the next patch, #186, will make this switchable.

[Copilot]

Pull request overview

This PR introduces a “rough” mechanism to allow switching a given pin back and forth between peripheral functions (UART/SPI/I2C/PWM/ADC/DAC) by re-initializing/de-initializing Zephyr devices when Arduino APIs begin/end or when analog/pinMode operations occur.

Changes:

• Add explicit device init() calls in Wire.begin(), SPI.begin(), and Serial.begin().
• Add optional device deinit() calls in Wire.end(), SPI.end(), and Serial.end() when CONFIG_DEVICE_DEINIT_SUPPORT is enabled.
• Add a per-pin “last device” tracker and _reinit_peripheral_if_needed() helper used by pinMode(), analogWrite(), and analogRead() to re-init peripherals when switching pinmux usage.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
libraries/Wire/Wire.cpp	Re-initialize I2C device in begin(); deinit in end() behind CONFIG_DEVICE_DEINIT_SUPPORT.
libraries/SPI/SPI.cpp	Re-initialize SPI device in begin(); deinit in end() behind CONFIG_DEVICE_DEINIT_SUPPORT.
cores/arduino/zephyrSerial.h	Deinitialize UART device in end() behind CONFIG_DEVICE_DEINIT_SUPPORT.
cores/arduino/zephyrSerial.cpp	Re-initialize UART device at start of begin().
cores/arduino/zephyrInternal.h	Expose _reinit_peripheral_if_needed() as a C-linkage internal helper.
cores/arduino/zephyrCommon.cpp	Implement _reinit_peripheral_if_needed() and call it from pin/analog APIs to re-init pinmux-related peripherals.

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[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

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[soburi]

@DhruvaG2000

Could you please merge this?
I understand this is a temporary, transitional solution, but unless this is accepted,
and also #188 is included,
it will be difficult to incorporate the solution, arduino@bb610e7.