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/unlink_file_trailing_slashes.rs

@@ -0,0 +1,67 @@
+use std::{env, process};
+use wasi::wasi_unstable;
+use wasi_tests::open_scratch_directory;
+use wasi_tests::utils::{cleanup_dir, create_dir, create_file};
+use wasi_tests::wasi_wrappers::wasi_path_unlink_file;
+
+unsafe fn test_unlink_file_trailing_slashes(dir_fd: wasi_unstable::Fd) {
+    // Create a directory in the scratch directory.
+    create_dir(dir_fd, "dir");
+
+    // Test that unlinking it fails.
+    assert_eq!(
+        wasi_path_unlink_file(dir_fd, "dir"),
+        Err(wasi_unstable::EISDIR),
+        "unlink_file on a directory should fail"
+    );
+
+    // Test that unlinking it with a trailing flash fails.
+    assert_eq!(
+        wasi_path_unlink_file(dir_fd, "dir/"),
+        Err(wasi_unstable::EISDIR),
+        "unlink_file on a directory should fail"
+    );
+
+    // Clean up.
+    cleanup_dir(dir_fd, "dir");
+
+    // Create a temporary file.
+    create_file(dir_fd, "file");
+
+    // Test that unlinking it with a trailing flash fails.
+    assert_eq!(
+        wasi_path_unlink_file(dir_fd, "file/"),
+        Err(wasi_unstable::ENOTDIR),
+        "unlink_file with a trailing slash should fail"
+    );
+
+    // Test that unlinking it with no trailing flash succeeds.
+    assert_eq!(
+        wasi_path_unlink_file(dir_fd, "file"),
+        Ok(()),
+        "unlink_file with no trailing slash should succeed"
+    );
+}
+
+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_unlink_file_trailing_slashes(dir_fd) }
+}