Reorganize wasi-misc-tests. (#575)

* Reorganize wasi-misc-tests.

Move wasi-misc-tests out of wasi-common, to break a dependency cycle;
previously, wasmtime-* depended on wasi-common, but wasi-common
dev-dependended on wasmtime-*.

Now, wasi-common no longer dev-depends on wasmtime-*; instead, the
tests are in their own crate which depends on wasi-common and on
wasmtime-*.

Also, rename wasi-misc-tests to wasi-tests for simplicity.

This also removes the "wasm_tests" feature; it's replaced by the
"test-programs" feature.

* Update the CI script to use the new feature name.

* Update the CI script to use the new feature name in one more place.

* Change a `write!` to a `writeln!`.

crates/test-programs/wasi-tests/src/bin/remove_nonempty_directory.rs

@@ -0,0 +1,50 @@
+use std::{env, process};
+use wasi::wasi_unstable;
+use wasi_tests::open_scratch_directory;
+use wasi_tests::utils::{cleanup_dir, create_dir};
+use wasi_tests::wasi_wrappers::wasi_path_remove_directory;
+
+unsafe fn test_remove_nonempty_directory(dir_fd: wasi_unstable::Fd) {
+    // Create a directory in the scratch directory.
+    create_dir(dir_fd, "dir");
+
+    // Create a directory in the directory we just created.
+    create_dir(dir_fd, "dir/nested");
+
+    // Test that attempting to unlink the first directory returns the expected error code.
+    assert_eq!(
+        wasi_path_remove_directory(dir_fd, "dir"),
+        Err(wasi_unstable::ENOTEMPTY),
+        "remove_directory on a directory should return ENOTEMPTY",
+    );
+
+    // Removing the directories.
+    assert!(
+        wasi_path_remove_directory(dir_fd, "dir/nested").is_ok(),
+        "remove_directory on a nested directory should succeed",
+    );
+    cleanup_dir(dir_fd, "dir");
+}
+
+fn main() {
+    let mut args = env::args();
+    let prog = args.next().unwrap();
+    let arg = if let Some(arg) = args.next() {
+        arg
+    } else {
+        eprintln!("usage: {} <scratch directory>", prog);
+        process::exit(1);
+    };
+
+    // Open scratch directory
+    let dir_fd = match open_scratch_directory(&arg) {
+        Ok(dir_fd) => dir_fd,
+        Err(err) => {
+            eprintln!("{}", err);
+            process::exit(1)
+        }
+    };
+
+    // Run the tests.
+    unsafe { test_remove_nonempty_directory(dir_fd) }
+}