configs/configupgrade: Use mock provider instead of test provider
configs/configupgrade: Use mock provider instead of test provider

The test provider comes with a lot of baggage since it's designed to be
used as a plugin, so instead we'll just use the mock provider
implementation directly, and so we can (in a later commit) configure it
appropriately for what our tests need here.

iljaskevic/terraform,tpounds/terraform,VladRassokhin/terraform,rnaveiras/terraform,VladRassokhin/terraform,pryorda/terraform,apparentlymart/terraform,pradeepbhadani/terraform,mattray/terraform,iljaskevic/terraform,pradeepbhadani/terraform,youhong316/terraform,pdecat/terraform,drebes/terraform,apparentlymart/terraform,brandontosch/terraform,VladRassokhin/terraform,ewbankkit/terraform,pradeepbhadani/terraform,drebes/terraform,pryorda/terraform,ewbankkit/terraform,hashicorp/terraform,brandontosch/terraform,brandontosch/terraform,nlamirault/terraform,heimweh/terraform,mattray/terraform,mattray/terraform,tommynsong/terraform,tpounds/terraform,youhong316/terraform,iljaskevic/terraform,gechr/terraform,luis-silva/terraform,ewbankkit/terraform,heimweh/terraform,tommynsong/terraform,pdecat/terraform,nlamirault/terraform,ewbankkit/terraform,tpounds/terraform,drebes/terraform,tpounds/terraform,rnaveiras/terraform,heimweh/terraform,pryorda/terraform,luis-silva/terraform,tommynsong/terraform,hashicorp/terraform,apparentlymart/terraform,pdecat/terraform,gechr/terraform,mattray/terraform,apparentlymart/terraform,pdecat/terraform,gechr/terraform,heimweh/terraform,youhong316/terraform,heimweh/terraform,VladRassokhin/terraform,apparentlymart/terraform,nlamirault/terraform,iljaskevic/terraform,youhong316/terraform,hashicorp/terraform,drebes/terraform,brandontosch/terraform,luis-silva/terraform,luis-silva/terraform,rnaveiras/terraform,brandontosch/terraform