Wizard changes for next cairo-contracts release

[ericglau]

Breaking changes that affect Wizard:

• Refactor directory structure cairo-contracts#335

Release branch: cairo/next

Release checklist (after cairo-contracts is released):

• Update contractsVersion string in https://github.com/OpenZeppelin/contracts-wizard/blob/cairo/next/packages/core-cairo/src/utils/version.ts to the latest released version number of cairo-contracts
• Merge branch cairo/next to master
• Release new version of @openzeppelin/wizard-cairo to npm from packages/core-cairo
  • Update version in packages/core-cairo/CHANGELOG.md
  • Bump package version (to 0.4.0 since it's a breaking change), tag, and publish, e.g:

yarn config set version-tag-prefix "@openzeppelin/wizard-cairo@"
yarn config set version-git-message "Publish @openzeppelin/wizard-cairo@%s"
yarn version
git push upstream --tags master
npm publish