Feature/stm32 i2c v1 slave mode

[HybridChild]

Summary

Implements I2C MultiMaster (Slave) functionality for STM32 v1 hardware.

Changes

• Blocking slave operations: blocking_listen(), blocking_respond_to_read(), blocking_respond_to_write()
• Async slave operations with DMA: listen(), respond_to_read(), respond_to_write()
• Robust error handling and transaction termination detection
• Example code for both blocking and async
• Rename FrameOptions enum to OperationFraming and add documentation

Testing

Tested on STM32F401RE Nucleo board with Digilent Analog Discovery acting as I2C Master.

I2C frequency: 100kHz
Slave address: 0x42 (7-bit)

• ✅ Basic Write and Read operations
• ✅ Write-Read combined transactions with RESTART
• ✅ Variable-length transfers: Pad with 0x00 when Master read exceeds buffer size
• ✅ Variable-length transfers: Discard bytes when Master write exceeds buffer size

Related Issues

stm32/i2c: slave mode support #622