Improve Reactor Netty compression support configuration

[bclozel]

This was partially solved by #10782.
Since then, Reactor Netty has refactored its HTTP compression support with reactor/reactor-netty#282 and reactor/reactor-netty#298.

We should align with those simplifications and ignore the server.compression.min-response-size option.

If reactor/reactor-netty#218 is fixed, we should in this case align compression configuration with other servers and apply a similar strategy than UndertowCompressionConfigurer.

Note: the server.compression.min-response-size option is only applied if the HTTP response sent by the application contains a Content-Length header. By default, Spring WebFlux uses Transfer-Encoding: chunked responses to avoid buffering the whole response. (see SPR-16542 for possible improvements on that).