http-client-branch: remove some degenerate test cases from BufferingSubscriberTest

http-client-branch: more debugging, and hopefully a fix, for a FlowTest intermittent failure (ERROR AT END)

http-client-branch: minor doc formatting

http-client-branch: (WebSocket) builder change

http-client-branch: review comment asFileImpl sneaked into the API

http-client-branch: more precision for GET() in HttpRequest.Builder

http-client-branch: more precision for headers in HttpRequest.Builder

http-client-branch: minor doc formatting in HttpRequest

http-client-branch: moved noBody() to HttpRequest.BodyPublisher

http-client-branch: better diagnosis of expected exceptions