ATSAMD21 is pulling ports low when calling wire.onRequest()

The intent: Using the controller and I2C for turning a port high and low and querying for data from an agent.

The setup: Two Adafruit Itsybitsy M0 Express, but tested on the MKRWIFI1010 as well to same result so this seems to be ATSAMD21 specific. Testing with a NANO EVERY the problem does not occur. Connected via I2C, 4k7 pullups on SDA/SCL. Working example that shows the bug:

Controller:

```
//CONTROLLER
#include

uint8_t data[6];

void setup()
{
Wire.begin(); //start I2C
}

void loop()
{
enablePort(0x22);
delay(10);
fetch(0x22);
delay(90);
disablePort(0x22);
delay(100);
}

void fetch(uint8_t add)
{
Wire.requestFrom(add,6,1); //address, quantity, bus release
uint8_t n = 0;
while(Wire.available())
{
data[n] = Wire.read();
n++;
}
}

void enablePort(uint8_t port)
{
uint8_t send_status = 1;
while(send_status != 0)
{
Wire.beginTransmission(port);
Wire.write(1);
send_status = Wire.endTransmission();
}
}

void disablePort(uint8_t port)
{
uint8_t send_status = 1;
while(send_status != 0)
{
Wire.beginTransmission(port);
Wire.write(0);
send_status = Wire.endTransmission();
}
}
```
Agent:

```
//AGENT
#include

uint8_t buffer[6] = {1,2,3,4,5,6};

void setup()
{
Wire.begin(0x22); //join I2C Bus
Wire.onRequest(sendData); //what to do when being talked to
Wire.onReceive(receiveEvent); //what to do with data received

pinMode(13,OUTPUT);
}

void loop() {}

void sendData()
{
Wire.write(buffer,6);
}

void receiveEvent(int bytes_incoming)
{
byte c = Wire.read();
if(c == 1)
{
digitalWrite(13,HIGH);
}
else
{
digitalWrite(13,LOW);
}
}
```
What should happen: D13 (the LED) should alternately go high and low with a 100ms interval.

What actually happens: The Port is pulled high only for 10ms and when the function fetch() is called, the port is immediately pulled low.

Start by reproducing the controller/agent example on ATSAMD21 boards and compare it with the NANO EVERY behavior. Trace the Wire.requestFrom() and Wire.onRequest() paths involved in the transaction, then verify that D13 remains high until disablePort() and that the provided I2C data is still returned.

Written by the indexing model from the issue text.