EmberApplicationInstance willDestroy in settled.ts uses the wrong `internalPendingRequests`

[raycohen]

upon updating ember-test-helpers, I have test code that resets the app hit the app instance willDestroy method, which errors on internalPendingRequests.clearPendingRequests() because internalPendingRequests is the (nonzero) integer result of calling the pendingRequests method.

Here's where the pendingRequests method is chained on the require that prevents accessing the other methods:

ember-test-helpers/addon-test-support/@ember/test-helpers/settled.ts

Lines 30 to 31 in 9c6e884

	return loader.require('ember-testing/lib/test/pending_requests')
	.pendingRequests;

error occurs here:

ember-test-helpers/addon-test-support/@ember/test-helpers/settled.ts

Line 59 in 9c6e884

internalPendingRequests.clearPendingRequests();

likewise the off calls are passing undefined since internalPendingRequests is an integer and not a module

If you look at the deleted code in #1047 it was not chaining pendingRequests on the old require('ember-testing/lib/test/pending_requests') which allowed accessing the different methods from that module.

Is a PR welcome here?