AK+Everywhere: Change AK::fill_with_random to accept a Bytes object

Rather than the very C-like API we currently have, accepting a void* and
a length, let's take a Bytes object instead. In almost all existing
cases, the compiler figures out the length.

Userland/Libraries/LibCrypto/Curves/X25519.cpp

@@ -30,7 +30,7 @@ static void conditional_swap(u32* first, u32* second, u32 condition)
 ErrorOr<ByteBuffer> X25519::generate_private_key()
 {
     auto buffer = TRY(ByteBuffer::create_uninitialized(BYTES));
-    fill_with_random(buffer.data(), buffer.size());
+    fill_with_random(buffer);
     return buffer;
 }