support linux io_uring

[Xudong-Huang]

[Mek101]

May I suggest an interface based/inspired upon AsyncBufRead?
https://without.boats/blog/io-uring/

Basically the "caller borrowing a mutable buffer to the interface" doesn't work really well with io_uring, and since io_uring itself can manage buffers, putting the existing model upside-down with the caller borrowing from the interface, may be the best option