refactor: use makeStream for creating AsyncStream with continuation (… #515

Job	Run time
GraphQL \| Auth Directive Tests	0s
GraphQL \| Lazy Load Tests	0s
GraphQL \| IAM Tests	0s
GraphQL \| User Pool Tests	0s
REST \| User Pool Tests	0s
Functional Tests / API Integration Tests \| Functional (iOS) / iOS Tests \| AWSAPIPluginFunctionalTests	11m 19s
Functional Tests / API Integration Tests \| Functional (watchOS) / watchOS Tests \| AWSAPIPluginFunctionalTestsWatch	8m 23s
Functional Tests / API Integration Tests \| Functional (tvOS) / tvOS Tests \| AWSAPIPluginFunctionalTests	9m 18s
GraphQL \| Lambda Tests / API Integration Tests \| GraphQL Lambda (iOS) / iOS Tests \| AWSAPIPluginGraphQLLambdaAuthTests	11m 29s
GraphQL \| Lambda Tests / API Integration Tests \| GraphQL Lambda (tvOS) / tvOS Tests \| AWSAPIPluginGraphQLLambdaAuthTests	9m 10s
GraphQL \| Lambda Tests / API Integration Tests \| GraphQL Lambda (watchOS) / watchOS Tests \| AWSAPIPluginGraphQLLambdaAuthTestsWatch	6m 24s
REST \| IAM Tests / API Integration Tests \| REST IAM (iOS) / iOS Tests \| AWSAPIPluginRESTIAMTests	7m 35s
REST \| IAM Tests / API Integration Tests \| REST IAM (watchOS) / watchOS Tests \| AWSAPIPluginRESTIAMTestsWatch	6m 49s
REST \| IAM Tests / API Integration Tests \| REST IAM (tvOS) / tvOS Tests \| AWSAPIPluginRESTIAMTests	5m 24s
	1h 15m 51s

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