boards: shields: introduce SparkFun u-blox SARA-R4 shield

SparkFun offers an Arduino-R3 compatible shield using the SARA-R410M-02B
LTE Cat M1/NB-IoT modem.

Now, that the basic SARA-R4 modem driver is implemented, let's enable
the shield for several MCUs supporting Arduino-R3 compatible headers.

Product Link:
https://www.sparkfun.com/products/14997



Signed-off-by: Michael Scott <mike@foundries.io>