ArduinoCore-API deployment

[Aymane-ST]

Summary

This PR integrates the official ArduinoCore-API
as a git submodule under cores/arduino/api/, aligning STM32duino with the
official Arduino ecosystem standard

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Motivation

This integration:

• Aligns STM32duino with official Arduino API contracts
• Enables seamless use of modern Arduino libraries targeting ArduinoCore-API
• Introduces type-safe enums (PinMode, PinStatus, pin_size_t) that
  eliminate invalid-value bugs
• Keeps all STM32-specific extensions fully intact

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Commits Summary

Commit	Description
b288540	Add ArduinoCore-API as git submodule in cores/arduino/api
2e1f2f1	CI: script to sync and rework ArduinoCore-API submodule
5280b5c	CI: patch to update README with STM32duino integration info
4c1ea78	CI: patch to implement weak _write() hook for Print
0f54255	CI: change variant_generic template to generate pin_size_t analogInputPin[]
38e21ae	feat(core): switch to ArduinoCore-API foundation (enums and types)
aa6beed	CI: update workflow to support submodule
d200d64	feat(serial): switch to ArduinoCore-API usage
8eb97a7	feat(wire): switch to ArduinoCore-API usage
8ab7061	feat(spi): switch to ArduinoCore-API usage
782c249	feat(timer): switch to ArduinoCore-API usage
c2e3e30	feat(servo): switch to ArduinoCore-API usage
64b0e10	feat(rgbled): switch to ArduinoCore-API usage

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What Changed

Submodule

• ArduinoCore-API is tracked as a git submodule at cores/arduino/api/
• Pinned to a stable upstream commit; synced via CI script

Core Types & Enums

• Switched from raw uint32_t to pin_size_t, PinMode, PinStatus
• Backward-compatible: legacy #define HIGH/OUTPUT/... macros preserved

Peripheral Migration

Each peripheral now inherits from the official abstract interface:

• Uart(old HardwareSerial) → arduino::HardwareSerial — all pure virtuals implemented,
  STM32 extensions (setRx, setTx, setHalfDuplex, flow control...) preserved
• TwoWire → arduino::HardwareI2C — STM32 pin remapping extensions preserved
• SPIClass → arduino::HardwareI2C — pin remapping (setMISO, setMOSI,
  setSCLK, setSSEL) preserved
• Servo, Timer, RGBled — updated to use API types

CI / Tooling

• Submodule-aware CI workflow
• Sync script to rework submodule state cleanly

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Related

• ArduinoCore-API: https://github.com/arduino/ArduinoCore-API
• STM32 Patches for ArduinoCore-API https://github.com/stm32duino/ArduinoCore-API
• Fixes feat: ArduinoCore-API deployment #2852.

[fpistm]

LGTM. Thanks @Aymane-ST .
Under test.