This commit adds support for the new `ReactorResourceFactory` and
ensures that such a bean is created and destroyed with the application
context. This will create a `ClientHttpConnector` bean, to be configured
on the `WebClient.Builder` instance - or let developers create their own
`ClientHttpConnector` bean to override that opinion.

By default, the `ReactorResourceFactory` is configured to participate
with the global resources, for better efficiency.

Closes gh-14058