SpringBoot Add support for RestClient

Framework now include a new RestClient with a similar design to WebClient (see https://github.com/spring-projects/spring-framework/issues/29552). We should add support for it, including SSL Bundle support.

Comment From: poutsma

See https://github.com/spring-projects/spring-boot/pull/36213

Comment From: philwebb

Closing in favor of PR #36213