Check for an active RequestContext before accessing ResteasyReactiveLocaleResolver#currentVertxRequest to prevent ContextNotActiveException

I addes only 1 test in `integration-tests\hibernate-validator-resteasy-reactive` module because `extensions\hibernate-validator\deployment` doesn't use `resteasy-reactive` which is a mandatory module to raise the problem.

I'm also looking to reproduce the problem in our backend code with some `@RestClient`s interaction but takes time.

Fixes #31434