Prior to this commit, the `WebClientExchangeTags`, when given a request
without a string template, would only get the request path to create the
"uri" tag for metrics. This is inconsistent with the
`RestTemplateExchangeTags`, which are taking the full request URI minus
the protocol+host+port.
This commit aligns the `WebClientExchangeTags` behavior in this case.
Closes gh-22832