Instrument AWS SDK Swift

[pokryfka]

• Remove dependency on aws-sdk-swift
• Instrument AWS Swift Modules
  • extend HTTP client API to pass BaggageContext?
  • extend their API to pass BaggageContext?
• Update AWSXRaySDKExampleAWS

see proof of the concept HTTP client slashmo/gsoc-swift-tracing#95 created as part of #16

[pokryfka]

PoC here soto-project/soto-core#348

uses AHC swift-server/async-http-client#289

will need to wait for swift-tracing to be released