This commit adds a new chain-based, interception contract to be used
with `WebClient`. This is the HTTP client equivalent of the `WebFilter`
contract already implemented in web reactive server.
A `ClientHttpRequestInterceptor` implementation can transform the
outgoing HTTP request (method, URI or headers) before delegating it to
the next interceptor in the chain, or bypass the request processing
altogether and return a (cached) HTTP response.
Issue: SPR-14502
5b33e02fb4