Asynchronous DMA transfers in Arduino_Bus

[calint]

I have a draft of a patch that implements:

Arduino_Bus:
virtual bool asyncDMASupported();
virtual bool asyncDMAIsBusy();
virtual void asyncDMAWaitForCompletion();
virtual void asyncDMAWriteBytes(uint8_t *data, uint32_t len);

and implementation for:
Arduino_ESP32SPI
Arduino_ESP32SPIDMA

tested on ESP32-2432S028R with doubled performance in use case.

Kind regards

[calint]

and now implementation for:
Arduino_ESP32QSPI

tested on JC4827W543R with roughly doubled performance in use case.

Kind regards

[calint]

Pull request #475