Changed TokenController._createEthersContract to no longer be async

[BelfordZ]

TokensController touch ups

The main change in this PR is removal of async from the TokensController._createEthersContract interface, since it does not make any async calls, it does not need to return a promise.

Description

• BREAKING:

  • _createEthersContract, though prefixed with an underscore, is very much a public function that could be used by others. That said, no longer returning a promise could be considered a breaking change.

• FIXED:

  • Clean up use of sinon
    • keep track of stubs and directly restore vs. using global sinon.restore and hoping for the best.
    • prefer jest mocks over sinon in select places
    • add better typing to TokensController._createEthersContract
    • restore clock / sinon.useFakeTimers manually for to maintain sanity

• REMOVED:

  • remove unnecessary await (dont make sync methods that return promises):
    1. call to tokenStateChangeListener
    2. interface for TokensController._createEthersContract.
  3. call to tokensController._getNewAllTokensState from tests.

• ADDED:

  • create mock / test helper for TokenController (for now only mocking createEthersContract).
    • More DRY testing code, easy to build upon

Checklist

• [ x ] Tests are included if applicable
• [ x ] Any added code is fully documented

[mcmire]

Good change — just had a few suggestions.

[mcmire]

Looks good to me!