Spring Upgrade to Reactor Dysprosium SR5

As part of upgrade arounds for: * https://github.com/reactor/reactor-netty/issues/948 in ErrorHandlerIntegrationTests * https://github.com/reactor/reactor-core/issues/1925 (if available) in StringDecoder

Comment From: rstoyanchev

I'm going to re-purpose this from SR4 to SR5 since the main upgrade points from the description are not yet available.