[Java][Flight] Add caching of FlightClients to JDBC

### Describe the enhancement requested

When getFlightInfo reports a list of endpoints, the driver internally creates a FlightClient for each endpoint that reports a Location. These clients can benefit from being cached/pooled since a server will likely re-use endpoints for subsequent queries. This should likely be a configuration option.

The driver should also check if the Location at an endpoint is the same as the original location used when calling getFlightInfo and avoid creating a new FlightClient in this case.

Investigate using https://github.com/ben-manes/caffeine for caching.

### Component(s)

FlightRPC, Java

首先追蹤 Java JDBC 驅動程式的 getFlightInfo 路徑，並調查它如何為傳回的 Locations 建立 FlightClients。依照建議調查 Caffeine，然後定義用於用戶端快取或集區化的設定選項，並驗證原始 Location 會被重複使用，而不會建立重複的用戶端。完成的標準是：後續查詢會重複使用端點用戶端，且原始 Location 不會導致建立額外的用戶端。

由索引模型根據 Issue 內容生成。