Loading code in the validator

[Mirko-von-Leipzig]

This also makes me realize is that we may not need to request code from the store (as we do in #1521). Nothing to change now, but may be good to create an issue so that we don't forget about it later.

Originally posted by @bobbinth in #1570 (review)

[bobbinth]

Actually, I mixed up the validator and the NTX builder. So, this issue is not really relevant.