XRayInstrument should map HTTP Span attributes to XRay segment HTTP

[pokryfka]

XRayInstrument should try to map HTTP Span attributes to XRay Segment HTTP request metadata

see comparison of XRay segment against OT Span

[pokryfka]

Currently all OT attributes are logged as annotations or metadata, example:

{
  "service" : {
    "version" : "aws-xray-sdk-swift"
  },
  "end_time" : 1595597689.3613839,
  "id" : "d0fae7e50034a757",
  "annotations" : {
    "http.method" : "GET",
    "http.url" : "https:\/\/aws.amazon.com",
    "http.response_content_length" : 212445,
    "http.status_code" : "200"
  },
  "start_time" : 1595597687.7261341,
  "trace_id" : "1-5759e988-bd862e3fe1be46a994272793",
  "name" : "HTTP https:\/\/aws.amazon.com"
}