opcode: add Futex{Wake,Wait,Waitv}

[oxalica]

These opcodes are available since Linux 6.7, and are mentioned by #253. FutexWaitV expects a new struct futex_waitv which is available in linux-raw-sys. An opaque type is added to the main crate to avoid polling in the dependency.

See:

• IORING_OP_FUTEX_{WAIT,WAKE}: torvalds/linux@194bb58
• IORING_OP_FUTEX_WAITV: torvalds/linux@8f35019

[quininer]

Thanks. This looks pretty good!

[oxalica]

Exposed types::FutexWaitV and also fixed a typo in tests (waitv, not wakev).

I noticed that io-uring-test fails test_udp_recvmsg_multishot_trunc on my machine (io-uring-test/src/tests/net.rs:1549:25, assertion failed: msg.is_payload_truncated()), not sure if it's something kernel related (I'm on 6.9.0-rc2). But at least it seems unrelated.

[quininer]

LGTM

[quininer]

Thank you!