Issue: SPR-15072

Issue: SPR-15071

Issue: SPR-15069

Issue: SPR-14692
Issue: SPR-15067

When connecting with a ReconnectStrategy we can only report the outcome
of the first connect to the ListenableFuture<Void> return value.

Failures for all subsequent attempts to reconnect however must be
channeled to TcpConnectHandler#afterConnectFailure which is used in
the STOMP broker relay for example to publish
BroadcastAvailability(true/false) events.

When decoding STOMP messages unread portions of a given input ByteBuf
must be kept until more input is received and the next complete STOMP
frame can be parsed.

In Reactor Net 2.x this was handled for us through the "remainder"
field in NettyChannelHandlerBridge. The Reactor Netty 0.6 upgrade
however applied only a simple map operator on the input ByteBuf
after which the buffer is relased.

This commit replaces the use of a simple map operator for decoding
and installs a ByteToMessageDecoder in the Netty channel pipeline
which has a built-in ability to preserve and merge unread input into
subsequent input buffers.

https://github.com/reactor/reactor-netty/issues/22

Issue: SPR-15060

Issue: SPR-14912

Issue: SPR-14892
Issue: SPR-15042

Issue: SPR-15047

reactor-netty-0.6.0.RELEASE on Maven Central depends on
reactor-ipc-0.6.0.RELEASE so no need for this repository anymore.

It may be needed to cleanup Gradle or Maven local cache
since preliminary version of reactor-netty-0.6.0.RELEASE
had a dependency on reactor-ipc-0.6.0.BUILD-SNAPSHOT.

Issue: SPR-15001

This commit removes the statically created XnioWorker which is an
"active" component and should not be created automatically and could
lead to resource leaks. Instead XnioWorker is now required at
construction aligning better with WebSocketClient#connectionBuilder
which also does not have a "default" worker option.

Since the XnioWorker is the main input for creating a ConnectionBuilder
we now create the ConnectionBuider in a protected method and then allow
a Consumer<ConnectionBuilder> to configure it further as opposed to the
Function<URI, ConnectionBuilder> used previously.

This commit also removes default SSL context initialization for RxNetty
to better align with other client implementations.

Issue: SPR-14527

Issue: SPR-15055

Includes streamlined ClassPathBeanDefinitionScanner setup.

Issue: SPR-14654

Issue: SPR-15052

Issue: SPR-15056

Issue: SPR-15054

Issue: SPR-14675

Issue: SPR-15053

Issue: SPR-15048

Issue: SPR-14097

Issue: SPR-14505

Issue: SPR-8704