AK: Implement SipHash as the default hash algorithm for most use cases

SipHash is highly HashDoS-resistent, initialized with a random seed at
startup (i.e. non-deterministic) and usable for security-critical use
cases with large enough parameters. We just use it because it's
reasonably secure with parameters 1-3 while having excellent properties
and not being significantly slower than before.

AK/HashTable.h

@@ -114,6 +114,9 @@ private:
     BucketType* m_bucket { nullptr };
 };
 
+// A set datastructure based on a hash table with closed hashing.
+// HashTable can optionally provide ordered iteration when IsOrdered = true.
+// For a (more commonly required) map datastructure with key-value entries, see HashMap.
 template<typename T, typename TraitsForT, bool IsOrdered>
 class HashTable {
     static constexpr size_t grow_capacity_at_least = 8;