Vertex AI MCP client fails on Reactive runtime

[sidutti]

The VertexAiGeminiChatModel does not subscribe on bounded elastic and fail as .block() gets called in the MCP client implementation.

This has been addressed for few models in this issue with commit.

Can the same be applied to VertexAI as well?
Proposed change:
in the method internalStream

Flux<ChatResponse> chatResponse1 = Flux.fromStream(responseStream.stream())
		.switchMap(response2 -> Mono.just(response2).map(response -> {
			List<Generation> generations = response.getCandidatesList()
				.stream()
				.map(this::responseCandidateToGeneration)
				.flatMap(List::stream)
				.toList();
		return new ChatResponse(generations, toChatResponseMetadata(response));
})).subscribeOn(Schedulers.bounderedElastic());