Need a better way to set `ioprio` flags on SQE

[rrichardson]

We would like to set IORING_RECVSEND_POLL_FIRST on the SQE. This is a flag that is set in the ioprio field in a similar fashion as IORING_RECVSEND_BUNDLE

I don't think it's scalable to keep adding Opcodes that are combinations of these flags and others. This flag is pretty much orthogonal to all other flags. It doesn't require special handling or operations.

Maybe we can just expose ioprio on the Entry struct using bitfield/Flags?

[silvanshade]

Maybe we can just expose ioprio on the Entry struct using bitfield/Flags?

Usually the ioprio should be exposed on the opcode (before building the SQE), if supported:

https://docs.rs/io-uring/latest/io_uring/opcode/struct.Read.html#method.ioprio

[rrichardson]

I see. So we just need a PR to add that to Send, SendZc, Recv, and maybe some others? It looks like it is present on SendMsg and RecvMsg.