Move migrate to flowkit

[bjartek]

Instructions

Issue To Be Solved

Migrate is implemented in internal package and it is thus impossible to compose upon it in other tools. All of the state it depends upon is in flowkit, so it should be in flowkit

(Optional): Suggest A Solution

Move it to flowkit

(Optional): Context

Testing migrations of contracts using overflow

[ianthpun]

i'll take this

[ianthpun]

Given the migration is atually somehting that will be scrapped post-crescendo, im thinking we can just keep it here and remove it once its finished. I'd like to keep flowkit as core as it gets, unless its blocking you somehow @bjartek ?

[chasefleming]

Closing this for now. Let me know if you need it @bjartek and it should be reopened.