Add support for `poll_oneoff` calls which just sleep on a relative timeout. This fixes a bug handling code compiled with WASI libc's `sleep` family of functions, which call `poll_oneoff` with a `CLOCK_REALTIME` timer, which wasn't previously implemented.
This is the test-programs crate, which builds and runs whole programs
compiled to wasm32-wasi.
To actually run these tests, the test-programs feature must be enabled, e.g.:
cargo test --features test-programs/test_programs --package test-programs