GrapheneIntegration: Track operation name for tracing

[keithhackbarth]

It is helpful to have the operation's name if trying to track the individual performance of GraphQL transactions using Sentry. This PR implements the approach suggested in this article, as part of the GrapheneIntegration()

Note: I looked and wasn't initially sure how to write a good test for this and also wasn't sure if this PR is even a good idea in the first place. So leaving a light version here for feedback.

[czyber]

Hi @keithhackbarth, i would love to see this change! Mind if I look into writing tests for it on the weekend?

[czyber]

Hey @keithhackbarth, i added a test and made a PR on your fork 😄