Previously, some classes that were annotatated with
@ConditionalOnWebApplication assumed that, if the application was a
web application, Spring MVC (spring-webmvc) would be on the classpath.
If it was not, the application would fail to start, typically with an
error relating to WebMvcConfigurerAdapter being unavailable.

This commit updates the affected configuration classes and annotates
them with @ConditionalOnClass(WebMvcConfigurerAdapter.class) to
ensure that their auto-configuration only takes effect if its a web
application and Spring MVC is on the classpath.

Fixes gh-2345