Finishing the I2C embargo

It looks like the I2C embargo is almost done. I think to close it off we should open an issue to track all the bugs or untested acks that made it through due to lack of hardware or complexity of fixing the bug. I think the embargo should require the I2C API adaption but not require fixes to bugs that exist in master (though many of these problems were solved).

Can we start a tracking issue for all the bugs/untested on hw acks that currently exist and finish the embargo so we don't block any longer (https://github.com/RIOT-OS/RIOT/issues/9518)?