Can you current-limit Arduino 101 GPIO pins?
No. I have never heard of a microcontroller with constant current or current limiting on the GPIO pins.

You may get a drive strength on the pins of an FPGA, but I have never seen such a thing on a microcontroller.

In general, if you have a need to reduce the voltage as the current increases you would just slip a resistor in the circuit. Or for more precise control using the GPIO pin to control a constant current source or constant current sink is the normal way of doing it.

GPIO pins are generally designed for communicating with other logic level devices. They require minimal current. Some microcontrollers provide a higher drive strength to work with larger fanouts (lots of devices connected to one pin, such as in SPI buses), but they are not intended for providing power to a device or giving control over their current.