Export apollo-link-test-utilities

[thetrevorharmon]

Overview

Export the Apollo link test utilities found in graphql-testing for clients to use them.

Motivation

What inspired this enhancement? What makes you think this should be in quilt?

If you look across Shopify's repos, there are many repos that have copy+pasted this code for their own use. Considering that the package is named graphql-testing, I think it's the logical thing for them to be exported out of the package to be used by other repos in the org.

Checklist

• Please delete the labels section before submitting your issue
• I have described this issue in a way that is actionable (if possible)