[Feature] _serial_fifo_rx in serial.c can be better

Describe problem solved by the proposed feature

_serial_fifo_rx with RT_SERIAL_RX_BLOCKING in serial.c is limited by the buffer size
1.when needed size is large than ringbuffer size, _serial_fifo_rx will do nothing.
2.when needed size is large than readable size, _serial_fifo_rx will update rx_fifo->rx_cpt_index = size and wait for rx_fifo->rx_cpt, but do nothing else.
The above results in data loss.

Describe your preferred solution

_serial_fifo_rx with RT_SERIAL_RX_BLOCKING in serial.c, maybe can waiting for dma intrrupt event to copy readable data to user buffer several times, until readed data size is enough. When readable size is large then user read size, data can be copied directly.

Describe possible alternatives

No response

Start in serial.c at _serial_fifo_rx and trace the RT_SERIAL_RX_BLOCKING path, including how readable data and DMA interrupt events are handled. Check the ringbuffer-size and partial-readable-data cases described in the issue. Done means blocking reads can copy data in multiple DMA-driven steps until the requested size is met, without losing data.