Fix Play-ws stream() bug

[randomanderson]

This pull request fixes a bug in the play-ws instrumentation where calls to .stream() lead to a separate wrapper class being needed (#1252 ). Requiring these lines be added:

      if (asyncHandler instanceof StreamedAsyncHandler) {
        asyncHandler = new StreamedAsyncHandlerWrapper((StreamedAsyncHandler) asyncHandler, span);
      } else {
        asyncHandler = new AsyncHandlerWrapper(asyncHandler, span);
      }

Additionally, this pull request:

• Refactors common code from the play-ws projects into a base project
• Adds tests for the 4 ways play-ws can be used (java, java stream, scala, scala stream)
• Adds a chunked encoding test to the HttpClientTest

Unfortunately, the tests also exposed a bug in the play-ws and/or scala promises instrumentation where callbacks to a promise aren't executed in the correct context. I added a flag to that HttpClientTest along with a //FIXME comment

[tylerbenson]

A lot going on here, but nothing stands out. I appreciate the additional testing.

... looks like there are some test failures to work through first though.

[randomanderson]

A lot going on here, but nothing stands out. I appreciate the additional testing.

... looks like there are some test failures to work through first though.

@tylerbenson It was a lot more straightforward before the refactor but the amount of copy/pasting was killing me. It probably should have been 2 separate PRs