Implements IDekiSPI with buses and the devices on them. SPIBusComponent is a boot step that starts one bus from its pins, and every device on it then shares that bus with a chip select, clock and mode of its own. A device can read at a slower clock than it writes, and can use a three-wire bus where data goes both ways on one pin. The platform package supplies the backend; on ESP32 that is deki-esp32-integration.
Every component it adds, every exported property and its changelog are in the deki-spi reference.