[Flight] Make it possible to use native gRPC Java APIs, and/or simplify the implementation

### Describe the enhancement requested

https://github.com/grpc/grpc-java/pull/10318 introduces a new type of blocking stub in grpc-java which handles streaming calls. This could drastically simplify DoGet/DoPut/DoExchange which try to present blocking interfaces to nonblocking APIs. However, preferably we would make it possible to use gRPC APIs directly instead of making users wait for us to wrap new APIs in even less documented new APIs. Also, it's not clear that this simplifies the server side at all (unfortunately).

首先審查 grpc-java PR 10318 以及 issue 中描述的 Flight DoGet、DoPut 和 DoExchange 介面。比較使用原生阻塞式 streaming API 與目前 wrappers 的方案，同時考量伺服器端的影響。完成應表示已明確選擇一種方案，該方案要麼支援直接使用 gRPC API，要麼能夠明確簡化實作。

由索引模型根據 Issue 內容生成。