go graphql: Add ability to override HTTP graphql executor
go graphql: Add ability to override HTTP graphql executor

Summary: I don't think this executor is used anywhere, but I'd rather
have a common change across the board to use the new ExecutorWrapper
api.

samsarahq/thunder,samsarahq/thunder,samsarahq/thunder,samsarahq/thunder,samsarahq/thunder