[Flight client] Allow disabling the creation of a child allocator

### Describe the enhancement requested

`FlightClient` [always creates a child allocator](https://github.com/apache/arrow-java/blob/7cbf15994ae7c82fbcb178dded6b3f128219d9ad/flight/flight-core/src/main/java/org/apache/arrow/flight/FlightClient.java#L86). While this is good in the general case to track memory leaks, this prevents usage scenarios where vectors live longer than the Flight client.

What about adding a `FlightClient.Builder#createChildAllocator(boolean)` that would allow users to choose whether they want a child allocator (current behavior which will be the default) or directly use the provided one?

I can create a PR for this.

Comece em flight/flight-core/src/main/java/org/apache/arrow/flight/FlightClient.java, por volta da linha 86, e siga FlightClient.Builder. Verifique se o comportamento padrão ainda cria um allocator filho, enquanto a nova opção pode usar diretamente o allocator fornecido. Está concluído quando ambos os modos de allocator estiverem cobertos pelos testes relevantes do cliente Flight.

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