ArrowBuf copying from GetReadableBuffer causes slowness

### Describe the usage question you have. Please include as many useful details as possible.

I'm using Arrow Flight and discovered an extra copy action while testing performance impact.

` ReadableBuffer readableBuffer = fastPath ? getReadableBuffer(stream) : null;
if (readableBuffer != null) {
readableBuffer.readBytes(buf.nioBuffer(0, size));
} `

The flame graph shows that after enabling zero_copy, ArrowBuf copying from GetReadableBuffer causes slowness.
Why does this copy occur?
Or is it because arrowbuf needs to manage its own memory, so the ownership must be transferred from netty?

### Component(s)

FlightRPC

从 issue 中展示的 FlightRPC 快速路径开始，沿着 getReadableBuffer 经过 ReadableBuffer.readBytes 跟踪到 ArrowBuf 目标，同时对照报告中的火焰图。确定复制是否是所有权或内存管理所必需的，并记录原因，或记录一种有明确支持的避免复制的方法。

由索引模型根据 Issue 内容生成。