Strict Concurrency Support

[mgacy]

• Enables strict concurrency checking
• Updates dependencies
  • Note that swift-aws-lambda-events v 0.3.0 dropped its custom implementation of HTTP types in favor of the standard Swift HTTP Type project.

Other

• Removes the SwiftLint plugin dependency and instead uses a workflow with the danger-swiftlint action. Since this action's Docker image already contains Danger-Swift and our standard Dangerfile doesn't use any additional plugins, there is appaently no need to create an additional SwiftPM build target that requires Danger.