cleanup optimistic updates tests

[joshribakoff]

please reference an issue where a consensus about the design was reached (not necessary for small changes)

#3712

[apollo-cla]

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[apollo-cla]

	Fails
🚫	No CHANGELOG added.

	Warnings
⚠️	❗ Big PR

Generated by 🚫 dangerJS

[joshribakoff]

@hwillson

I was able to flatten the complex test case! I find this much easier to understand. Please see Before and After.

I first tried to use zen-observable.reduce for this, but it did not work [because it messed with the internal state of QueryObservable]. I'll only use rxjs for the tests, not in any production code for the scope of this PR...

Please let me know if this looks good I'll finish up the rest of the optimist tests!

[joshribakoff]

I finished the will handle dependent updates refactoring. All tests are passing. Circle CI simply warns there is no changelog.

While working on these tests, I ran into this odd issue I wrote up here.

#3723

This PR could now be merged and I can do another PR later on to flatten the rest of the tests.

[hwillson]

Thanks very much for working on this @joshribakoff, and sorry for the delay getting this merged! Everything looks👌, so we'll have this merged shortly. Thanks again!