Avoid codec auto-configuration when they are not going to be used

[wilkinsona]

CodecsAutoConfiguration is conditional on CodecConfigurer which is part of spring-web. This means that the auto-configuration will kick in for any typical web application. This is somewhat at odds with the codecs only being used, I think, by WebClient and WebFlux. We should see if we can tighten up the conditions so that CodecsAutoConfiguration (and its inner configurations JacksonCodecConfiguration and LoggingCodecConfiguration) only kick in when more likely to be used.