Allow actuator endpoint selectors to capture all paths

[philwebb]

The @Selector annotation allows endpoints to capture path segments when exposed over the web. For example void find(@Selector String one, @Selector String two) will be mapped to /<root>/<endpoint>/find/{one}/{two}.

For some endpoints, it would be nice if we could capture all remaining path segments rather than limit ourselves to one. For example it would be nice if we could write void find(@MultiSelector String[] segments) and have it mapped to /<root>/<endpoint>/find/{*segements}. If a call such as /<root>/<endpoint>/find/spring/boot would invoke the method with a segments value of {"spring", "boot"}.

[philwebb]

#14022 would be one example where we could use this.