LibCore: Expose file type from DirIterator

Our `find` utility makes use of the `dirent::d_type` field for filtering
results, which `Core::DirIterator` didn't expose. So, now it does. :^)

We now store the name and type of the entry as the "next" value instead
of just the name. The type is exposed as a `DirectoryEntry::Type`
instead of a `DT_FOO` constant, so that we're not tied to posixy
systems, and because proper enums are nice. :^)

Userland/Libraries/LibCore/DirectoryEntry.h

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2023, Sam Atkins <atkinssj@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/DeprecatedString.h>
+
+struct dirent;
+
+namespace Core {
+
+struct DirectoryEntry {
+    enum class Type {
+        BlockDevice,
+        CharacterDevice,
+        Directory,
+        File,
+        NamedPipe,
+        Socket,
+        SymbolicLink,
+        Unknown,
+        Whiteout,
+    };
+    Type type;
+    // FIXME: Once we have a special Path string class, use that.
+    DeprecatedString name;
+
+    static DirectoryEntry from_dirent(dirent const&);
+};
+
+}