Add a new `ClientHttpConnectorBuilder` interface to support the
creation of `ClientHttpConnector` instances. The new code is similar
to the `ClientHttpRequestFactoryBuilder` interface that was added to
Spring Boot 3.4.
The `ClientHttpConnectorBuilder` is a functional interface with
additional static factory methods for the various supported
`ClientHttpConnector` types. Each type has it's own builder
which to support client specific customization.
The previous auto-configuration has been relocated to the
`org.springframework.boot.autoconfigure.http.client.reactive`
package and updated to make use of the builder.
Closes gh-43079
983e7b637b