Migrate tests to jest

[promaty]

Jest supports typescript out of the box without any extra configuration, while doing it in mocha is very awkward:
https://github.com/aragon/protocol-backend/blob/f38fcccd52cb74b3a39ffa0b21c4de0ca9524cef/packages/server/test/helpers/babel-ts.js

Also it allows creating more powerful mocks with property matchers, which I don't think can be done in mocha+chai:
https://github.com/aragonone/ipfs-pinner/blob/development/packages/server/test/integration/file-creation.test.ts#L24