Remove all direct usage of webdriver.promise

[sjelin]

Currently I'm shifting things from new wdpromise.Promise() and wdpromise.fulfilled() to flow.promise() and wdpromise.when(). These functions are useful because they instance a ManagedPromise when the control flow is enabled, but a native ES6 promise when the control flow is disabled.

However, when the control flow is completely removed from selenium-webdriver many of the helper functions will go away. The when() function and SimpleScheduler will certainly go away.

We have two options:

1. Create a helper file promiseUtils.ts which has its own version of
   • wdpromise.when()
   • wdpromise.all()
   • wdpromise.controlFlow()
   • flow.promise()
   • etc.
2. Wait until selenium-webdriver removes the control flow entirely and then transition over to the ES6 native functions
   • Promise.fulfill()
   • Promise.all()
   • null (there is no ES6 equivalent to the control flow)
   • new Promise()
   • etc.

Option 2 is certainly more standard, it has some disadvantages:

• It cannot be started until the control flow is totally removed, as it would break any users relying on the control flow
• During the period of time while we wait for the control flow to be removed, these functions may be deprecated.
• If we decide to do Feature Request: Allow users to use a custom ControlFlow/scheduler #4024, we're going to have to write our own mini version of SimpleScheduler anyway.

Option 1 is what jasmine did in angular/jasminewd#82, but that's largely because jasminewd isn't tied to a specific version of selenium-webdriver like Protractor is.