Stop using deprecated NoStackTraceThrowable in vertx-core internals

[jnbdz]

Motivation

Fixes #5012.

NoStackTraceThrowable and NoStackTraceException are @Deprecated(forRemoval = true), and 17bad9d introduced the transition path: users should catch/observe VertxException instead, with the class removal itself planned for Vert.x 6.

However vertx-core internals still instantiate NoStackTraceThrowable, so failures created from a message (Promise#fail(String), Promise#tryFail(String), Future#failedFuture(String), Completable#fail(String)) or from a null cause still surface the deprecated type at runtime.

Changes

• Replace the internal instantiations in Completable, Promise, FailedFuture and FutureImpl with the equivalent VertxException.noStackTrace(...) factory. Message and no-stack-trace behaviour are unchanged; the runtime type broadens to VertxException (the direct superclass and the documented replacement). NoStackTraceException has no remaining usage.
• The deprecated classes themselves are left untouched for removal in Vert.x 6, per 17bad9d. Happy to remove them in this PR instead if that is preferred for 5.2.
• NoStackTraceTimeoutException is intentionally out of scope: it is not deprecated and must remain a java.util.concurrent.TimeoutException for the HTTP client timeout contract.
• Tests: FutureTest now pins the failure contract (VertxException exact class, message preserved, empty stack trace) for the message/null-cause paths.
• Additional test coverage: the shared HttpClientTimeoutTest suite now also runs over HTTP/3 (Http3ClientTimeoutTest wired through Http3Configurator) and asserts that client request timeout failures are TimeoutException instances carrying no stack trace across HTTP/1, HTTP/2 and HTTP/3. HTTP/3 tests relying on behaviours not yet available (pool saturation semantics, client re-creation from HttpClientOptions, request idle timeout on streams) are @Ignored with documented reasons.

Compatibility

Code catching VertxException (the documented replacement) is unaffected since NoStackTraceThrowable extends VertxException. Only instanceof NoStackTraceThrowable checks observe the change, which is the pattern the deprecation instructs migrating away from.

[jnbdz]

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