Improve how HTTP message writers are obtained for general use vs for
multipart requests.

Functionally equivalent updates to package private classes to improve
the code and make it easier to understand.

This commit makes it possible to pass attributes from the WebSession of
a handshake request to the WebSocketSession, by configuring a
Predicate<String> on HandshakeWebSocketService.

Issue: SPR-16212

Issue: SPR-16212

Issue: SPR-16844

Issue: SPR-16531

Issue: SPR-16843

Issue: SPR-16831

Issue: SPR-16830

Issue: SPR-16820

Issue: SPR-16829

Issue: SPR-16820

After the recent changes to expose configuring TcpOperations, it no
longer makes sense to automatically log the relayHost/Port since that's
mutually exclusive with a custom TcpOperations.

Instead we delegate to TcpOperations.toString().

Issue: SPR-16801

Issue: SPR-16804

Issue: SPR-16531

Issue: SPR-16829

Issue: SPR-16811

Issue: SPR-16816

Issue: SPR-16826

Issue: SPR-16803

Issue: SPR-16429

Issue: SPR-16823

Issue: SPR-16303

Issue: SPR-16411

Issue: SPR-16804

Issue: SPR-16805

Issue: SPR-16318

Includes upgrade to Netty 4.1.25, Undertow 2.0.7, Hibernate ORM 5.1.14.

Issue: SPR-15407

Issue: SPR-16513

Issue: SPR-16808

DefaultMultipartHttpServletRequest always returned mulitpart parameter
values only rather than aggregating with query parameters, which
contradicts with Servlet spec, section 3.1, and is inconsistent with
StandardMultipartHttpServletRequest.

Issue: SPR-16590