Remove typenames from MockedProvider

[carlows]

This PR allows to pass a removeTypenames prop to the MockedProvider, this way there's no need to add the __typename field to the mocked data.

Right now, to add mocked data in tests, it's required to use addTypenameToDocument in all of the queries:

const query = addTypenameToDocument(HERO_QUERY);

Together with this, the mocked data needs to include the __typename field in all of the models:

export const hero_no_friends = {
  __typename: 'Droid',
  name: 'r2d2',
  id: '1',
  friends: null,
};

I find this a bit of a pain, and I would prefer not having to do this. As the apollo-client accepts an addTypename field, we can allow the MockedProvider to configure that option as we'd like.

This can be used this like this:

<MockedProvider mocks={mocks} removeTypename>

I didn't find any tests for test-utils, so I only added an example test within the base example.

[apollo-cla]

@carlows: Thank you for submitting a pull request! Before we can merge it, you'll need to sign the Meteor Contributor Agreement here: https://contribute.meteor.com/

[mention-bot]

@carlows, thanks for your PR! By analyzing the history of the files in this pull request, we identified @jbaxleyiii, @calebmer and @mmissey to be potential reviewers.

[apollo-cla]

	Warnings
⚠️	There are library changes, but not tests. That's OK as long as you're refactoring existing code

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[jbaxleyiii]

@carlows this is such a great addition 😍

Thank you! And congrats on your first contribution here!