Previously we only required synchronization points where blocks were
sent between nodes; now we need them between action and query operations
on the same node, because wallet notification of mined blocks no longer
occurs in real-time.
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.