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;
+    }
 };
 
 }

Tests/AK/TestByteBuffer.cpp

@@ -7,6 +7,7 @@
 #include <LibTest/TestCase.h>
 
 #include <AK/ByteBuffer.h>
+#include <AK/Vector.h>
 
 TEST_CASE(equality_operator)
 {
@@ -33,6 +34,18 @@ TEST_CASE(equality_operator)
     EXPECT_EQ(d == d, true);
 }
 
+TEST_CASE(byte_buffer_vector_contains_slow_bytes)
+{
+    Vector<ByteBuffer> vector;
+    ByteBuffer a = ByteBuffer::copy("Hello, friend", 13).release_value();
+    vector.append(a);
+
+    ReadonlyBytes b = "Hello, friend"sv.bytes();
+    Bytes c = a.bytes();
+    EXPECT_EQ(vector.contains_slow(b), true);
+    EXPECT_EQ(vector.contains_slow(c), true);
+}
+
 BENCHMARK_CASE(append)
 {
     ByteBuffer bb;