This commit introduces a new variant of web applications: there are now
Servlet based and Reactive web applications.
The mere presence of `Servlet` and `ConfigurableWebApplicationContext`
classes is not enough to make a difference between those variants.
This is why the decision process is now the following:
* if `DispatcherHandler` is present but not `DispatcherServlet`, the
WebApplicationType is detected as REACTIVE
* if `DispatcherHandler` is present and `DispatcherServlet`, this is a
case where we consider that developers are using Spring MVC in
combination with the reactive web client. So WebApplicationType is
detected as SERVLET
* if `Servlet` and `ConfigurableWebApplicationContext` are present,
WebApplicationType is detected as SERVLET
* if none of the above match, WebApplicationType is NONE
Fixes gh-8017
250a1601d7