Possibly support FIONBIO flag in ioctl() for wasip2 sockets

https://github.com/WebAssembly/wasi-libc/pull/606 makes `ioctl()` return `ENOTSUP` when called with the `FIONBIO` flag in wasip2. @pchickey suggested that this operation should maybe be supported for sockets (though not files): https://github.com/WebAssembly/wasi-libc/pull/606#discussion_r2294949144