Support Ack Polling for I2C

When writing to an EEPROM (Microchip 24LC256), the device goes into a "busy" state for a few milliseconds when a page of data has been written. It is possible to "poll" the device to determine when it has finished by essentially performing a zero byte write, essentially meaning that the device address is sent on the bus, then if the device is ready it will acknowledge (ACK) and if it is not ready it will not acknowledge (NACK).

The issue is that there needs to be a way to poll the device to determine whether it is ready for the next command.

Ideal solution: add the following method to I2cDevice: `bool AckPoll()`, which sends only the device address on the bus and returns a boolean matching the ACK/NACK state. This can then be read in a tight loop to determine when the device is ready.
Could probably also be implemented as an awaitable async method with a timeout to do background polling, but the simple implementation is fine.

Note: I am not using the underlying OS support for I2c via `I2cDevice.Create()`, I have derived from I2cBus and I2cDevice to implement a Serial to I2C converter that works on any OS, so all my testing so far has been done using this running on Windows 10. The trivial implementation below _works_, in that a zero byte write that is not acknowleged by the device throws an exception stating "NACK on address" - it just takes too long to throw/catch the exception longer than the busy time of the device), hence the need for a *proper* AckPoll method that doesnt rely on catching exceptions (I am _assuming_ that the OS support for I2C works in the same way):

```
bool AckPoll()
{
try
{
i2cDevice.Write(new byte[0]);
return true;
}
catch
{
return false;
}
}
```