AK: Move the wildcard-matching implementation to StringUtils

Provide wrappers in the String and StringView classes, and add some tests.

AK/StringUtils.h

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <AK/Forward.h>
+
+namespace AK {
+
+enum class CaseSensitivity {
+    CaseInsensitive,
+    CaseSensitive,
+};
+
+namespace StringUtils {
+
+    bool matches(const StringView& str, const StringView& mask, CaseSensitivity = CaseSensitivity::CaseInsensitive);
+
+}
+
+}
+
+using AK::CaseSensitivity;