LibLocale: Move locale source files to the LibLocale folder

These are still included in LibUnicode, but this updates their location
and the include paths of other files which include them.

Userland/Libraries/LibLocale/PluralRules.cpp

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2022, Tim Flynn <trflynn89@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibLocale/PluralRules.h>
+
+namespace Locale {
+
+PluralForm plural_form_from_string(StringView plural_form)
+{
+    if (plural_form == "cardinal"sv)
+        return PluralForm::Cardinal;
+    if (plural_form == "ordinal"sv)
+        return PluralForm::Ordinal;
+    VERIFY_NOT_REACHED();
+}
+
+StringView plural_form_to_string(PluralForm plural_form)
+{
+    switch (plural_form) {
+    case PluralForm::Cardinal:
+        return "cardinal"sv;
+    case PluralForm::Ordinal:
+        return "ordinal"sv;
+    default:
+        VERIFY_NOT_REACHED();
+    }
+}
+
+PluralCategory __attribute__((weak)) determine_plural_category(StringView, PluralForm, PluralOperands)
+{
+    return PluralCategory::Other;
+}
+
+Span<PluralCategory const> __attribute__((weak)) available_plural_categories(StringView, PluralForm)
+{
+    static constexpr Array<PluralCategory, 1> categories { { PluralCategory::Other } };
+    return categories.span();
+}
+
+PluralCategory __attribute__((weak)) determine_plural_range(StringView, PluralCategory, PluralCategory)
+{
+    return PluralCategory::Other;
+}
+
+}