Do not block subscribers until the unsubscription request to RPC server
is completed. Otherwise, another notification may be received from the
RPC server which will block the unsubscription process.
At the same time, fix event-based waiter. We must not block the receiver
channel during unsubscription because there's a chance that subsequent
event will be sent by the server. We need to read this event in order not
to block the WSClient's readloop.
Hiding it behind blockchainer.Blockchain doesn't improve the testing system,
there is no other implementation of it that can fulfil all the needs of the
neotest and at the same time this limits the functions available to tests.
GAS and NEO tokens are sent to validators account (not the committee's
one). For single-node chain they are the same, but for four-nodes chain
they are different. Thus, use validators multisig address to create new
accounts and to deploy contracts.
Also, allow to provide desired account balance while creating new
account.
Sometimes user needs to construct transaction by itself, so it's better
to unify nonce sources for auto-generated and manually-generated
transactions to avoid nonce collisions in tests.
Implementing a separate `Signer` interface is beneficial in multiple
ways:
1. Support both single and multiple transaction witnesses.
2. It should be easy to add contract signer this way.
Tests should use accounts created with `NewAccount` so hiding all
details doesn't seem to be an issue.
Signed-off-by: Evgeniy Stratonikov <evgeniy@nspcc.ru>
