* Use fake provider for NetworkController unit tests
In the unit tests for NetworkController, it's important to prevent
network requests from occurring. Currently we do that by using Nock.
However, the `core` version of NetworkController uses a fake provider
object. This is arguably a better approach for unit tests because it
prevents us from having to think about the behavior that a specific
middleware may have. For instance, the Infura middleware intercepts
`eth_chainId` to return a static result, and the block cache middleware
replaces the `latest` block tag with the latest block number, making an
extra call to `eth_blockNumber` in doing so. We have to account for
these kinds of behaviors when using Nock, but we do not need to do this
when using a fake provider.
This should make it easier to compare the difference between the unit
tests in this repo vs. in the `core` repo, which should ultimately help
us merge the two controllers together.
* Rename fake-provider-engine to fake-provider
* Rearrange imports
* Move fake-provider and fake-block-tracker into a directory and exclude it from coverage
* Make FakeBlockTracker inert, and fix JSDocs
* Remove generics from FakeProvider
* Call beforeCompleting (and beforeResolving) using async/await
* Fix signature of sendAsync; align other signatures within FakeProvider
* No need to check whether error is not a string
* Don't exclude the provider-api-tests directory from coverage
* Make sure to mock both net_version and eth_getBlockByNumber when testing network status
* Fix FakeProvider so that none of the methods have optional callbacks
