Fix race condition that appears on fast repeated transfers.
Add public reset function. Because application code can stall the bus,
we need to give application code a way to fix itself.
This commit takes the fixes and error reporting improvements from
jcdickinson's work and applies them without overlaying a software state
machine on top of the hardware state machine.
Also allows configuration of response to 'general call' writes.
The RP2040 datasheet indicates that I2C pins should have a limited
slew rate (Page 440 - 4.3.1.3.). This configures that for both
`I2c` and `I2cSlave`.
In addition, the pin configuration has been centralized to a single
fn.
