Split http adapter logic out of the broker

[BryanFauble]

Items left before this can be moved out of draft state:

• engine.go: Determine the best way to pass along the context around the target adapter to the HTTP server. Since it's already being looked up in this code we shouldn't need to replicate the same code in the HTTP server, instead we should probably just pass along the context we found.
• Code to be deleted out of the broker
• sub_mgr.go: Is the implementation I wrote the best method to connect a request out to the HTTP server?
• http server, http_client.go: I need to get some context about the target adapter for the request in the SendEvent() function. I need to know the host, method, headers, ect...
• http server, http_client.go: When sending the response back - Will need to determine which is the correct timestamp to send back
• Testing a full round trip -- Currently the code will, Request from cURL -> http server -> broker -> quickstart component -> broker -> http server (Dies)

Problem:

1. The broker was responsible for executing HTTP requests that originate from components running the Kit SDK
2. Executing HTTP requests without a "/" in it was erroring out

Solution:

1. Copying the HTTP client code out of the broker and into the HTTP server running in the cluster
2. Adding in a "/" if the host if empty

Testing:
Verified that running the changes allowed me to execute a full round trip and receive a response:

{
  "args": {}, 
  "data": "", 
  "files": {}, 
  "form": {}, 
  "headers": {
    "Accept-Encoding": "gzip", 
    "Host": "httpbin.org", 
    "User-Agent": "Go-http-client/2.0", 
    "X-Amzn-Trace-Id": "Root=1-66663c6c-61460ac946f419545031d61b"
  }, 
  "json": null, 
  "method": "GET", 
  "origin": "98.225.110.56", 
  "url": "https://httpbin.org/anything"
}

[xadhatter]

Overall this looks great. Thanks again for all the work. It appears there is more work to fit the adapter into the existing component mold. But I think the best approach is to massage it so it does and have the broker treat it like any other component instead of making exceptions for adapters.