These features were deprecated at least 3 minor releases ago. I found
one mistake which was that `z_validateaddress` had not been placed
behind the `addrtype` deprecated feature; this has been fixed.
I tested the NU5 components of this PR by locally setting the protocol
version to 170014. I forgot to check that without that override, the
test would skip the NU5 checks. The reason it defaulted to NU5 is that
the test was reading the client version 4040150, which is indeed not
less than the NU5 protocol version ^_^;;
The p2p_nu_peer_management and rewind_index RPC tests still start from
Sprout, because they are explicitly (and only) testing network behaviour
across network upgrades.
The mempool_tx_input_limit test is removed because the flag has been
ignored since Sapling activation, and will be removed at some point in
the near future.