SPI API add void transfer(const void *tx_buffer, void *rx_buffer, size_t count);

### API component

SPI API

### Description

SPI API add
```
virtual void transfer(const void *tx_buffer, void *rx_buffer, size_t count);
```
[Expand SPI API and Functionality for High Speed Devices](https://github.com/arduino/ArduinoCore-API/discussions/189)

### Is this a breaking change?

Unlikely

### Additional information

This is really a missing API method, it doesn't make sense to have only a single buffer for both transmit and receive, as DMA hardware normally works in 2 buffers.
The plain old
https://github.com/arduino/ArduinoCore-API/blob/master/api/HardwareSPI.h#L112
```
virtual void transfer(void *buf, size_t count) = 0;
```
forces hacks such as:
- allocate a temporary buffer
- do the DMA transfers receiving into the temporary buffer
- copy that temporary buffer data back into the address pointed by *buf*
wasting both memory and cpu cycles

从 api/HardwareSPI.h 中现有的单缓冲区传输声明开始，然后阅读链接的讨论，以了解 SPI API 预期的范围。在更改接口之前，跟踪受影响的 API 实现和验证路径。完成的标准是：无需临时缓冲区 workaround，即可始终支持双缓冲区虚拟传输签名。

由索引模型根据 Issue 内容生成。