Add I3C Support library

[Aymane-ST]

Summary

This PR introduces an I3C library for STM32 .

Current scope includes:

• I3C controller mode
• I3C target mode
• Common Command Code (CCC) helpers
• Dynamic Address Assignment (DAA) and discovery helpers
• In-Band Interrupt (IBI) support
• Mixed bus support with I2C controller-side transfers

Supported STM32 families

Currently supported families:

• STM32H5xx
• STM32U3xx

Implemented features

Controller mode

• controller initialization and timing setup
• configurable controller startup options
• default private I3C SDR transfers:
  • write
  • read
  • writeReg
  • readReg
  • writeRegBuffer
  • readRegBuffer

Legacy I2C on mixed I3C bus

• explicit helper API:
  • i2cWrite
  • i2cRead
  • i2cWriteRead
  • i2cWriteReg
  • i2cReadReg
  • i2cWriteRegBuffer
  • i2cReadRegBuffer
  • scanI2CDevices
  • isI2CDeviceReady
• unified same-name overloads using I3CTransferType

CCC helpers

• broadcast/direct write and direct read helpers
• high-level wrappers for:
  • RSTDAA
  • DISEC
  • SETAASA
  • SETDASA
  • GETPID
  • GETBCR
  • GETDCR
  • event configuration (ENEC / DISEC)

Discovery / dynamic addressing

• DAA helpers
• discovery API for:
  • unknown devices only
  • known devices + optional unknown discovery
• known-device matching by static address or PID
• dynamic address allocation helpers

Target mode

• target initialization and configuration
• private receive/transmit helpers
• target-side notification support
• IBI request support

Controller-side IBI

• target device configuration for IBI handling
• controller-side IBI enable/disable
• polling and callback access to received IBI events

Internal structure

The implementation is split into:

• I3C.cpp: controller/target/CCC/discovery/IBI core logic
• I3C_I2C.cpp: legacy I2C-over-I3C helpers and unified transport overloads

The public API remains exposed through a single I3C.h header.

Files added

Main additions:

• libraries/I3C/src/I3C.h
• libraries/I3C/src/I3C.cpp
• libraries/I3C/src/I3C_I2C.cpp

Examples and build integration were also updated accordingly.

[fpistm]

LGTM for a first version

[cparata]

I'm wondering if it is better to move the I3C examples for LPS22DF directly on the LPS22DF library. I think that it is better to avoid the dependency inside the Core on the LPS22DF library. What about this proposal?

[fpistm]

OK for me. I will update the PR as @Aymane-ST is OoO.