Docs: reinstate serverless deployment guides

[trevor-scheer]

We should reintroduce (and update) our deployment guides for getting Apollo Server up and running in the popular serverless frameworks (lambda, azure, cloud, ...others?)

@glasser proposed a one-size-fits-most approach using @vendia/serverless here which we should lean in to:
apollo-server-integrations/apollo-server-integration-aws-lambda#38

We can suggest more specific implementations secondarily or as an "advanced usage" (i.e. @as-integrations/aws-lambda for users who are concerned about bundle size).

[trevor-scheer]

Consider incorporating changes proposed by #5675 if Azure guide is reinstated.

[rkoron007]

For context: right now I'm working on updating our AS3 Lambda guide to use @as-integrations/aws-lambda deploying using the Serverless framework to AWS Lambda. Hope to have a PR up before EOD. :)

[rkoron007]

PR for updating Lamda here: #7058

We could also add the @vendia/serverless-express package approach to the Integration Index page or add a separate "Serverless" integration article that'd show how to use @vendia/serverless-express and links out to the Lambda and Azure articles for details on how to use those integrations.