AK: Allow Vector<ByteBuffer>::contains_slow to accept (Readonly)Bytes

This is done by providing Traits<ByteBuffer>::equals functions for
(Readonly)Bytes, as the base GenericTraits<T>::equals is unable to
convert the ByteBuffer to (Readonly)Bytes to then use Span::operator==

This allows us to check if a Vector<ByteBuffer> contains a
(Readonly)Bytes without having to making a copy of it into a ByteBuffer
first. The initial use of this is in LibWeb with CORS-preflight, where
we check the split contents of the Access-Control headers with
Fetch::Infrastructure::Request::method() and static StringViews
such as "*"sv.bytes().

AK/ByteBuffer.h

@@ -332,6 +332,14 @@ struct Traits<ByteBuffer> : public GenericTraits<ByteBuffer> {
     {
         return Traits<ReadonlyBytes>::hash(byte_buffer.span());
     }
+    static bool equals(ByteBuffer const& byte_buffer, Bytes const& other)
+    {
+        return byte_buffer.bytes() == other;
+    }
+    static bool equals(ByteBuffer const& byte_buffer, ReadonlyBytes const& other)
+    {
+        return byte_buffer.bytes() == other;
+    }
 };
 
 }