[Slave] Support automatic PDO configuration + contiguous PDO memory mapping

[trns1997]

Add automatic PDO configuration support: read 0x1C12/0x1C13, follow 0x1600/0x1A00 mappings, build a contiguous in-memory PDO buffer, and provide helpers to copy that buffer to/from the ESC process-data and to pack/unpack into a C struct.