[#821] Update reference contracts

Description

Update reference contracts contracts/tezos_examples to their state in https://gitlab.com/tezos/tezos/-/tree/cb9f439e58c761e76ade589d1cdbd2abb737dc68/tests_python/contracts_013 (= tezos release 13.0, with jakarta support).
Additionally:

1. Moves reference contracts spread over morley repo to agree with their placement in the reference repo
   1. (mostly unparsable-by-morley contracts get moved from unparsable to tezos_examples/ill-typed)
   2. Drops some copyright headers not present in the original
   3. Documents unavoided discrepancies
2. Documents how to deal with unparsable and incorrectly typechecked contracts

Related issue(s)

Resolves #821 (closed)

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