Support non-USD currencies in the "Change price in cart" action

New currency field added that mostly uses the same code as the Adjustment action.

Not sure if an update hook is needed to insert a blank field value to existing configs.

This looks great, I chatted with @jurgenhaas in slack about the process and he said sites should run drush eca:update

I'll get to this once I have a moment.

nicxvan → credited jurgenhaas → .

Automatically closed - issue fixed for 2 weeks with no activity.