Use Apollo platform API

[pcarrier]

Migrate to the endpoint and schema we want publically documented and supported.

• Change the default endpoint URL;
• Migrate queries to the improved schema (renames like service → graph, and shape shifting like relocating fields from graph to variant rather than take a variant name argument);
• Minimally restructure the client code around the new response shapes;
• Quick fix for the git_context test relying on the repo's origin remote being the apollographql org, which eg gh repo fork breaks.
• Move from latestLaunch to latestApprovedLaunch when fetching supergraph SDL

[netlify]

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Name	Link
🔨 Latest commit	c6c780f

[EverlastingBugstopper]

this looks great!