Add tests for netlify graph + API Authentication

[anmonteiro]

Is your feature request related to a problem? Please describe.

We need to add a test for the Netlify Graph improvements made in #4167. We should test that for netlify dev --graph, the ONEGRAPH_AUTHLIFY_TOKEN variable gets injected into the environment.

Additionally, we'll wanna test that the event for function invocations contains an authlifyToken for users who've enabled API Authentication.