Add a name to the middleware function

[gsoltis]

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This is a small quality-of-life improvement. As the code comment says, some observability/instrumentation libraries rely on Function.name for the name of express middleware to use in a span. @opentelemetry/instrumentation-express is one example.

This PR returns a named function, rather than an anonymous function, and adds a test to ensure that the middleware is named.

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[glasser]

This functionality is now in separate packages (https://github.com/apollo-server-integrations/apollo-server-integration-express4 and https://github.com/apollo-server-integrations/apollo-server-integration-express5).